Steganographic messaging through imagery

ABSTRACT

Imagery is steganographically encoded with message data to serve a variety of purposes. For example, a photograph can be embedded with a message that identifies a corresponding record in a database, where the database record details information relating to the photograph (e.g., the photographer&#39;s name or address). Photocollages can be formed of plural photographic images, each encoded with a different steganographic message. Medical imagery can be embedded with steganographic messages, e.g., to aid in authentication of the images.

RELATED APPLICATION DATA

[0001] This application is a division of application Ser. No.09/479,304, filed Jan. 6, 2000, which claims priority to applicationSer. No. 09/172,324, filed Oct. 13, 1998 (now U.S. Pat. No. 6,064,737),which claims priority to application Ser. No. 08/637,531, filed Apr. 25,1996 (now U.S. Pat. No. 5,822,436). Application Ser. No. 08/637,531claims priority to applications Ser. No. 08/534,005, filed Sep. 25, 1995(now U.S. Pat. No. 5,832,119); Ser. No. 08/512,993, filed Aug. 9, 1995(now abandoned); Ser. No. 08/508,083, filed Jul. 27, 1995 (now U.S. Pat.No. 5,841,978); Ser. No. 08/436,102, filed May 8, 1995 (now U.S. Pat.No. 5,748,783); PCT/US94/13366, filed Nov. 16, 1994; Ser. No.08/327,426, filed Oct. 21, 1994 (now U.S. Pat. No. 5,768,426); Ser. No.08/215,289, filed Mar. 17, 1994 (now abandoned); and Ser. No.08/154,866, filed Nov. 18, 1993 (now abandoned). Priority under 35 USCSection 120 is claimed to each of these prior applications, and each isincorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates to images (e.g., photographs,medical imagery, etc.), and more particularly relates to images thatconvey steganographic messages.

SUMMARY OF THE INVENTION

[0003] According to one aspect of the invention, a photograph is encodedwith a steganographic message. This message serves to identify acorresponding record in a database, which database record detailsinformation relating to the photograph (e.g., the photographer's name).

[0004] According to another aspect, a photocollage is formed of pluralphotographic images, each encoded with a different steganographicmessage. Each steganographic message serves to associate a photographwith corresponding information (again, e.g., the correspondingphotographer's name).

[0005] According to yet another aspect, medical imagery is embedded witha steganographic message that aids in authentication of the image.

[0006] The foregoing and other features and advantages will be morereadily apparent from the following detailed description, which proceedswith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a simple and classic depiction of a one dimensionaldigital signal which is discretized in both axes.

[0008]FIG. 2 is a general overview, with detailed description of steps,of the process of embedding an “imperceptible” identification signalonto another signal.

[0009]FIG. 3 is a step-wise description of how a suspected copy of anoriginal is identified.

[0010]FIG. 4 is a schematic view of an apparatus for pre-exposing filmwith identification information in accordance with another embodiment ofthe present invention.

[0011]FIG. 5 is a diagram of a “black box” embodiment of the presentinvention.

[0012]FIG. 6 is a schematic block diagram of the embodiment of FIG. 5.

[0013]FIG. 7 shows a variant of the FIG. 6 embodiment adapted to encodesuccessive sets of input data with different code words but with thesame noise data.

[0014]FIG. 8 shows a variant of the FIG. 6 embodiment adapted to encodeeach frame of a videotaped production with a unique code number.

[0015] FIGS. 9A-9C are representations of an industry standard noisesecond that can be used in one embodiment of the present invention.

[0016]FIG. 10 shows an integrated circuit used in detecting standardnoise codes.

[0017]FIG. 11 shows a process flow for detecting a standard noise codethat can be used in the FIG. 10 embodiment.

[0018]FIG. 12 is an embodiment employing a plurality of detectors inaccordance with another embodiment of the present invention.

[0019]FIG. 13 shows an embodiment of the present invention in which apseudo-random noise frame is generated from an image.

[0020]FIG. 14 illustrates how statistics of a signal can be used in aidof decoding.

[0021]FIG. 15 shows how a signature signal can be preprocessed toincrease its robustness in view of anticipated distortion, e.g. MPEG.

[0022]FIGS. 16 and 17 show embodiments of the invention in whichinformation about a file is detailed both in a header, and in the fileitself.

[0023] FIGS. 18-20 show details relating to embodiments of the presentinvention using rotationally symmetric patterns.

[0024]FIG. 21 shows how the invention can be practiced by encoding“bumps” rather than pixels.

[0025] FIGS. 22-26 detail aspects of a security card according to oneembodiment of the present invention.

[0026]FIG. 27 is a diagram, illustrating the aspect of the inventionthat provides a network linking method using information embedded indata objects that have inherent noise.

[0027]FIG. 28 is a diagram of a photographic identification document orsecurity card with which the security system aspect of the presentinvention may be applied.

[0028]FIGS. 29 and 30 illustrate two embodiments by which subliminaldigital graticules can be realized.

[0029]FIGS. 31A and 31B show the phase of spatial frequencies along twoinclined axes.

[0030] FIGS. 32A-32C show the phase of spatial frequencies along first,second and third concentric rings.

[0031] FIGS. 33A-33E show steps in the registration process for asubliminal graticule using inclined axes.

[0032] FIGS. 34A-34E show steps in the registration process for asubliminal graticule using concentric rings.

[0033] FIGS. 35A-35C shows further steps in the registration process fora subliminal graticule using inclined axes.

[0034] FIGS. 36A-36D show another registration process that does notrequire a 2D FFT.

[0035]FIG. 37 is a flow chart summarizing a registration process forsubliminal graticules.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0036] In the following discussion of an illustrative embodiment, thewords “signal” and “image” are used interchangeably to refer to bothone, two, and even beyond two dimensions of digital signal. Exampleswill routinely switch back and forth between a one dimensionalaudio-type digital signal and a two dimensional image-type digitalsignal.

[0037] In order to fully describe the details of an illustrativeembodiment of the invention, it is necessary first to describe the basicproperties of a digital signal. FIG. 1 shows a classic representation ofa one dimensional digital signal. The x-axis defines the index numbersof sequence of digital “samples,” and the y-axis is the instantaneousvalue of the signal at that sample, being constrained to exist only at afinite number of levels defined as the “binary depth” of a digitalsample. The example depicted in FIG. 1 has the value of 2 to the fourthpower, or “4 bits,” giving 16 allowed states of the sample value.

[0038] For audio information such as sound waves, it is commonlyaccepted that the digitization process discretizes a continuousphenomena both in the time domain and in the signal level domain. Assuch, the process of digitization itself introduces a fundamental errorsource, in that it cannot record detail smaller than the discretizationinterval in either domain. The industry has referred to this, amongother ways, as “aliasing” in the time domain, and “quantization noise”in the signal level domain. Thus, there will always be a basic errorfloor of a digital signal. Pure quantization noise, measured in a rootmean square sense, is theoretically known to have the value of one overthe square root of twelve, or about 0.29 DN, where DN stands for DigitalNumber or the finest unit increment of the signal level. For example, aperfect 12-bit digitizer will have 4096 allowed DN with an innate rootmean square noise floor of about 0.29 DN.

[0039] All known physical measurement processes add additional noise tothe transformation of a continuous signal into the digital form. Thequantization noise typically adds in quadrature (square root of the meansquares) to the “analog noise” of the measurement process, as it issometimes referred to.

[0040] With almost all commercial and technical processes, the use ofthe decibel scale is used as a measure of signal and noise in a givenrecording medium. The expression “signal-to-noise ratio” is generallyused, as it will be in this disclosure. As an example, this disclosurerefers to signal to noise ratios in terms of signal power and noisepower, thus 20 dB represents a 10 times increase in signal amplitude.

[0041] In summary, the presently preferred embodiments of the inventionembed an N-bit value onto an entire signal through the addition of avery low amplitude encodation signal which has the look of pure noise. Nis usually at least 8 and is capped on the higher end by ultimatesignal-to-noise considerations and “bit error” in retrieving anddecoding the N-bit value. As a practical matter, N is chosen based onapplication specific considerations, such as the number of uniquedifferent “signatures” that are desired. To illustrate, if N=128, thenthe number of unique digital signatures is in excess of 10 38(2 128).This number is believed to be more than adequate to both identify thematerial with sufficient statistical certainty and to index exact saleand distribution information.

[0042] The amplitude or power of this added signal is determined by theaesthetic and informational considerations of each and every applicationusing the present methodology. For instance, non-professional video canstand to have a higher embedded signal level without becoming noticeableto the average human eye, while high precision audio may only be able toaccept a relatively small signal level lest the human ear perceive anobjectionable increase in “hiss.” These statements are generalities andeach application has its own set of criteria in choosing the signallevel of the embedded identification signal. The higher the level ofembedded signal, the more corrupted a copy can be and still beidentified. On the other hand, the higher the level of embedded signal,the more objectionable the perceived noise might be, potentiallyimpacting the value of the distributed material.

[0043] To illustrate the range of different applications to which theprinciples of the present invention can be applied, the presentspecification details two different systems. The first (termed, for lackof a better name, a “batch encoding” system), applies identificationcoding to an existing data signal. The second (termed, for lack of abetter name, a “real time encoding” system), applies identificationcoding to a signal as it is produced. Those skilled in the art willrecognize that the principles of the present invention can be applied ina number of other contexts in addition to these particularly described.

[0044] The discussions of these two systems can be read in either order.Some readers may find the latter more intuitive than the former; forothers the contrary may be true.

[0045] Batch Encoding

[0046] The following discussion of a first class of embodiments is bestprefaced by a section defining relevant terms:

[0047] The original signal refers to either the original digital signalor the high quality digitized copy of a non-digital original.

[0048] The N-bit identification word refers to a unique identificationbinary value, typically having N range anywhere from 8 to 128, which isthe identification code ultimately placed onto the original signal viathe disclosed transformation process. In the illustrated embodiment,each N-bit identification word begins with the sequence of values‘0101,’ which is used to determine an optimization of thesignal-to-noise ratio in the identification procedure of a suspectsignal (see definition below).

[0049] The m'th bit value of the N-bit identification word is either azero or one corresponding to the value of the m'th place, reading leftto right, of the N-bit word. E.g., the first (m=1) bit value of the N=8identification word 01110100 is the value 0; the second bit value ofthis identification word is ‘1’, etc.

[0050] The m'th individual embedded code signal refers to a signal whichhas dimensions and extent precisely equal to the original signal (e.g.both are a 512 by 512 digital image), and which is (in the illustratedembodiment) an independent pseudo-random sequence of digital values.“Pseudo” pays homage to the difficulty in philosophically defining purerandomness, and also indicates that there are various acceptable ways ofgenerating the “random” signal. There will be exactly N individualembedded code signals associated with any given original signal.

[0051] The acceptable perceived noise level refers to anapplication-specific determination of how much “extra noise,” i.e.amplitude of the composite embedded code signal described next, can beadded to the original signal and still have an acceptable signal to sellor otherwise distribute. This disclosure uses a 1 dB increase in noiseas a typical value which might be acceptable, but this is quitearbitrary.

[0052] The composite embedded code signal refers to the signal which hasdimensions and extent precisely equal to the original signal, (e.g. bothare a 512 by 512 digital image), and which contains the addition andappropriate attenuation of the N individual embedded code signals. Theindividual embedded signals are generated on an arbitrary scale, whereasthe amplitude of the composite signal must not exceed the pre-setacceptable perceived noise level, hence the need for “attenuation” ofthe N added individual code signals.

[0053] The distributable signal refers to the nearly similar copy of theoriginal signal, consisting of the original signal plus the compositeembedded code signal. This is the signal which is distributed to theoutside community, having only slightly higher but acceptable “noiseproperties” than the original.

[0054] A suspect signal refers to a signal which has the generalappearance of the original and distributed signal and whose potentialidentification match to the original is being questioned. The suspectsignal is then analyzed to see if it matches the N-bit identificationword.

[0055] The detailed methodology of this first embodiment begins bystating that the N-bit identification word is encoded onto the originalsignal by having each of the m bit values multiply their correspondingindividual embedded code signals, the resultant being accumulated in thecomposite signal, the fully summed composite signal then beingattenuated down to the acceptable perceived noise amplitude, and theresultant composite signal added to the original to become thedistributable signal.

[0056] The original signal, the N-bit identification word, and all Nindividual embedded code signals are then stored away in a securedplace. A suspect signal is then found. This signal may have undergonemultiple copies, compressions and decompressions, resamplings ontodifferent spaced digital signals, transfers from digital to analog backto digital media, or any combination of these items. If the signal stillappears similar to the original, i.e. its innate quality is notthoroughly destroyed by all of these transformations and noiseadditions, then depending on the signal to noise properties of theembedded signal, the identification process should function to someobjective degree of statistical confidence. The extent of corruption ofthe suspect signal and the original acceptable perceived noise level aretwo key parameters in determining an expected confidence level ofidentification.

[0057] The identification process on the suspected signal begins byresampling and aligning the suspected signal onto the digital format andextent of the original signal. Thus, if an image has been reduced by afactor of two, it needs to be digitally enlarged by that same factor.Likewise, if a piece of music has been “cut out,” but may still have thesame sampling rate as the original, it is necessary to register thiscut-out piece to the original, typically done by performing a localdigital cross-correlation of the two signals (a common digitaloperation), finding at what delay value the correlation peaks, thenusing this found delay value to register the cut piece to a segment ofthe original.

[0058] Once the suspect signal has been sample-spacing matched andregistered to the original, the signal levels of the suspect signalshould be matched in an rms sense to the signal level of the original.This can be done via a search on the parameters of offset,amplification, and gamma being optimized by using the minimum of themean squared error between the two signals as a function of the threeparameters. We can call the suspect signal normalized and registered atthis point, or just normalized for convenience.

[0059] The newly matched pair then has the original signal subtractedfrom the normalized suspect signal to produce a difference signal. Thedifference signal is then cross-correlated with each of the N individualembedded code signals and the peak cross-correlation value recorded. Thefirst four bit code (‘0101’) is used as a calibrator both on the meanvalues of the zero value and the one value, and on further registrationof the two signals if a finer signal to noise ratio is desired (i.e.,the optimal separation of the 0101 signal will indicate an optimalregistration of the two signals and will also indicate the probableexistence of the N-bit identification signal being present.) Theresulting peak cross-correlation values will form a noisy series offloating point numbers which can be transformed into 0's and 1's bytheir proximity to the mean values of 0 and 1 found by the 0101calibration sequence. If the suspect signal has indeed been derived fromthe original, the identification number resulting from the above processwill match the N-bit identification word of the original, bearing inmind either predicted or unknown “bit error” statistics. Signal-to-noiseconsiderations will determine if there will be some kind of “bit error”in the identification process, leading to a form of X% probability ofidentification where X might be desired to be 99.9% or whatever. If thesuspect copy is indeed not a copy of the original, an essentially randomsequence of 0's and 1's will be produced, as well as an apparent lack ofseparation of the resultant values. This is to say, if the resultantvalues are plotted on a histogram, the existence of the N-bitidentification signal will exhibit strong bi-level characteristics,whereas the non-existence of the code, or the existence of a differentcode of a different original, will exhibit a type of randomgaussian-like distribution. This histogram separation alone should besufficient for an identification, but it is even stronger proof ofidentification when an exact binary sequence can be objectivelyreproduced.

SPECIFIC EXAMPLE

[0060] Imagine that we have taken a valuable picture of two heads ofstate at a cocktail party, pictures which are sure to earn somereasonable fee in the commercial market. We desire to sell this pictureand ensure that it is not used in an unauthorized or uncompensatedmanner. This and the following steps are summarized in FIG. 2.

[0061] Assume the picture is transformed into a positive color print. Wefirst scan this into a digitized form via a normal high quality blackand white scanner with a typical photometric spectral response curve.(It is possible to get better ultimate signal to noise ratios byscanning in each of the three primary colors of the color image, butthis nuance is not central to describing the basic process.)

[0062] Let us assume that the scanned image now becomes a 4000 by 4000pixel monochrome digital image with a grey scale accuracy defined by12-bit grey values or 4096 allowed levels. We will call this the“original digital image” realizing that this is the same as our“original signal” in the above definitions.

[0063] During the scanning process we have arbitrarily set absoluteblack to correspond to digital value ‘30’. We estimate that there is abasic 2 Digital Number root mean square noise existing on the originaldigital image, plus a theoretical noise (known in the industry as “shotnoise”) of the square root of the brightness value of any given pixel.In formula, we have:

=sqrt(4+(V _(n,m)−30))   (1)

[0064] Here, n and m are simple indexing values on rows and columns ofthe image ranging from 0 to 3999. Sqrt is the square root. V is the DNof a given indexed pixel on the original digital image. The <>bracketsaround the RMS noise merely indicates that this is an expected averagevalue, where it is clear that each and every pixel will have a randomerror individually. Thus, for a pixel value having 1200 as a digitalnumber or “brightness value”, we find that its expected rms noise valueis sqrt(1204)=34.70, which is quite close to 34.64, the square root of1200.

[0065] We furthermore realize that the square root of the innatebrightness value of a pixel is not precisely what the eye perceives as aminimum objectionable noise, thus we come up with the formula:

=X*sqrt(4+(V _(n,m)−30) Y)   (2)

[0066] Where X and Y have been added as empirical parameters which wewill adjust, and “addable” noise refers to our acceptable perceivednoise level from the definitions above. We now intend to experiment withwhat exact value of X and Y we can choose, but we will do so at the sametime that we are performing the next steps in the process.

[0067] The next step in our process is to choose N of our N-bitidentification word. We decide that a 16 bit main identification valuewith its 65536 possible values will be sufficiently large to identifythe image as ours, and that we will be directly selling no more than 128copies of the image which we wish to track, giving 7 bits plus an eighthbit for an odd/even adding of the first 7 bits (i.e. an error checkingbit on the first seven). The total bits required now are at 4 bits forthe 0101 calibration sequence, 16 for the main identification, 8 for theversion, and we now throw in another 4 as a further error checking valueon the first 28 bits, giving 32 bits as N. The final 4 bits can use oneof many industry standard error checking methods to choose its fourvalues.

[0068] We now randomly determine the 16 bit main identification number,finding for example, 1101 0001 1001 1110; our first versions of theoriginal sold will have all 0's as the version identifier, and the errorchecking bits will fall out where they may. We now have our unique 32bit identification word which we will embed on the original digitalimage.

[0069] To do this, we generate 32 independent random 4000 by 4000encoding images for each bit of our 32 bit identification word. Themanner of generating these random images is revealing. There arenumerous ways to generate these. By far the simplest is to turn up thegain on the same scanner that was used to scan in the originalphotograph, only this time placing a pure black image as the input, thenscanning this 32 times. The only drawback to this technique is that itdoes require a large amount of memory and that “fixed pattern” noisewill be part of each independent “noise image.” But, the fixed patternnoise can be removed via normal “dark frame” subtraction techniques.Assume that we set the absolute black average value at digital number‘100’, and that rather than finding a 2 DN rms noise as we did in thenormal gain setting, we now find an rms noise of 10 DN about each andevery pixel's mean value.

[0070] We next apply a mid-spatial-frequency bandpass filter (spatialconvolution) to each and every independent random image, essentiallyremoving the very high and the very low spatial frequencies from them.We remove the very low frequencies because simple real-world errorsources like geometrical warping, splotches on scanners,mis-registrations, and the like will exhibit themselves most at lowerfrequencies also, and so we want to concentrate our identificationsignal at higher spatial frequencies in order to avoid these types ofcorruptions. Likewise, we remove the higher frequencies because multiplegeneration copies of a given image, as well as compression-decompressiontransformations, tend to wipe out higher frequencies anyway, so there isno point in placing too much identification signal into thesefrequencies if they will be the ones most prone to being attenuated.Therefore, our new filtered independent noise images will be dominatedby mid-spatial frequencies. On a practical note, since we are using12-bit values on our scanner and we have removed the DC valueeffectively and our new rms noise will be slightly less than 10 digitalnumbers, it is useful to boil this down to a 6-bit value ranging from−32 through 0 to 31 as the resultant random image.

[0071] Next we add all of the random images together which have a ‘1’ intheir corresponding bit value of the 32-bit identification word,accumulating the result in a 16-bit signed integer image. This is theunattenuated and un-scaled version of the composite embedded signal.

[0072] Next we experiment visually with adding the composite embeddedsignal to the original digital image, through varying the X and Yparameters of equation 2. In formula, we visually iterate to bothmaximize X and to find the appropriate Y in the following:

V _(dist;n,m) = _(orig;n,m) +V _(comp:n.m) *X*sqrt(4+V _(orin.n.m) Y)  (3)

[0073] where dist refers to the candidate distributable image, i.e. weare visually iterating to find what X and Y will give us an acceptableimage; orig refers to the pixel value of the original image; and comprefers to the pixel value of the composite image. The n's and m's stillindex rows and columns of the image and indicate that this operation isdone on all 4000 by 4000 pixels. The symbol V is the DN of a given pixeland a given image.

[0074] As an arbitrary assumption, now, we assume that our visualexperimentation has found that the value of X=0.025 and Y=0.6 areacceptable values when comparing the original image with the candidatedistributable image. This is to say, the distributable image with the“extra noise” is acceptably close to the original in an aesthetic sense.Note that since our individual random images had a random rms noisevalue around 10 DN, and that adding approximately 16 of these imagestogether will increase the composite noise to around 40 DN, the Xmultiplication value of 0.025 will bring the added rms noise back toaround 1 DN, or half the amplitude of our innate noise on the original.This is roughly a 1 dB gain in noise at the dark pixel values andcorrespondingly more at the brighter values modified by the Y value of0.6.

[0075] So with these two values of X and Y, we now have constructed ourfirst versions of a distributable copy of the original. Other versionswill merely create a new composite signal and possibly change the Xslightly if deemed necessary. We now lock up the original digital imagealong with the 32-bit identification word for each version, and the 32independent random 4-bit images, waiting for our first case of asuspected piracy of our original. Storage wise, this is about 14Megabytes for the original image and 32*0.5bytes*16 million=.about.256Megabytes for the random individual encoded images. This is quiteacceptable for a single valuable image. Some storage economy can begained by simple lossless compression.

[0076] Finding a Suspected Piracy of our Image

[0077] We sell our image and several months later find our two heads ofstate in the exact poses we sold them in, seemingly cut and lifted outof our image and placed into another stylized background scene. This new“suspect” image is being printed in 100,000 copies of a given magazineissue, let us say. We now go about determining if a portion of ouroriginal image has indeed been used in an unauthorized manner. FIG. 3summarizes the details.

[0078] The first step is to take an issue of the magazine, cut out thepage with the image on it, then carefully but not too carefully cut outthe two figures from the background image using ordinary scissors. Ifpossible, we will cut out only one connected piece rather than the twofigures separately. We paste this onto a black background and scan thisinto a digital form. Next we electronically flag or mask out the blackbackground, which is easy to do by visual inspection.

[0079] We now procure the original digital image from our secured placealong with the 32-bit identification word and the 32 individual embeddedimages. We place the original digital image onto our computer screenusing standard image manipulation software, and we roughly cut along thesame borders as our masked area of the suspect image, masking this imageat the same time in roughly the same manner. The word roughly is usedsince an exact cutting is not needed, it merely aids the identificationstatistics to get it reasonably close.

[0080] Next we rescale the masked suspect image to roughly match thesize of our masked original digital image, that is, we digitally scaleup or down the suspect image and roughly overlay it on the originalimage. Once we have performed this rough registration, we then throw thetwo images into an automated scaling and registration program. Theprogram performs a search on the three parameters of x position, yposition, and spatial scale, with the figure of merit being the meansquared error between the two images given any given scale variable andx and y offset. This is a fairly standard image processing methodology.Typically this would be done using generally smooth interpolationtechniques and done to sub-pixel accuracy. The search method can be oneof many, where the simplex method is a typical one.

[0081] Once the optimal scaling and x-y position variables are found,next comes another search on optimizing the black level, brightnessgain, and gamma of the two images. Again, the figure of merit to be usedis mean squared error, and again the simplex or other searchmethodologies can be used to optimize the three variables.

[0082] After these three variables are optimized, we apply theircorrections to the suspect image and align it to exactly the pixelspacing and masking of the original digital image and its mask. We cannow call this the standard mask.

[0083] The next step is to subtract the original digital image from thenewly normalized suspect image only within the standard mask region.This new image is called the difference image.

[0084] Then we step through all 32 individual random embedded images,doing a local cross-correlation between the masked difference image andthe masked individual embedded image. ‘Local’ refers to the idea thatone need only start correlating over an offset region of +/− 1 pixels ofoffset between the nominal registration points of the two images foundduring the search procedures above. The peak correlation should be veryclose to the nominal registration point of 0,0 offset, and we can addthe 3 by 3 correlation values together to give one grand correlationvalue for each of the 32 individual bits of our 32-bit identificationword.

[0085] After doing this for all 32 bit places and their correspondingrandom images, we have a quasi-floating point sequence of 32 values. Thefirst four values represent our calibration signal of 0101. We now takethe mean of the first and third floating point value and call thisfloating point value ‘0,’ and we take the mean of the second and thefourth value and call this floating point value ‘1.’ We then stepthrough all remaining 28 bit values and assign either a ‘0’ or a ‘1’based simply on which mean value they are closer to. Stated simply, ifthe suspect image is indeed a copy of our original, the embedded 32-bitresulting code should match that of our records, and if it is not acopy, we should get general randomness. The third and the fourthpossibilities of 3) Is a copy but doesn't match identification numberand 4) isn't a copy but does match are, in the case of 3), possible ifthe signal to noise ratio of the process has plummeted, i.e. the‘suspect image’ is truly a very poor copy of the original, and in thecase of 4) is basically one chance in four billion since we were using a32-bit identification number. If we are truly worried about 4), we canjust have a second independent lab perform their own tests on adifferent issue of the same magazine. Finally, checking the error-checkbits against what the values give is one final and possibly overkillcheck on the whole process. In situations where signal to noise is apossible problem, these error checking bits might be eliminated withouttoo much harm.

[0086] Benefits

[0087] Now that a full description of the first embodiment has beendescribed via a detailed example, it is appropriate to point out therationale of some of the process steps and their benefits.

[0088] The ultimate benefits of the foregoing process are that obtainingan identification number is fully independent of the manners and methodsof preparing the difference image. That is to say, the manners ofpreparing the difference image, such as cutting, registering, scaling,etcetera, cannot increase the odds of finding an identification numberwhen none exists; it only helps the signal-to-noise ratio of theidentification process when a true identification number is present.Methods of preparing images for identification can be different fromeach other even, providing the possibility for multiple independentmethodologies for making a match.

[0089] The ability to obtain a match even on sub-sets of the originalsignal or image is a key point in today's information-rich world.Cutting and pasting both images and sound clips is becoming more common,allowing such an embodiment to be used in detecting a copy even whenoriginal material has been thus corrupted. Finally, the signal to noiseratio of matching should begin to become difficult only when the copymaterial itself has been significantly altered either by noise or bysignificant distortion; both of these also will affect that copy'scommercial value, so that trying to thwart the system can only be doneat the expense of a huge decrease in commercial value.

[0090] An early conception of this invention was the case where only asingle “snowy images” or random signal was added to an original image,i.e. the case where N=1. “Decoding” this signal would involve asubsequent mathematical analysis using (generally statistical)algorithms to make a judgment on the presence or absence of this signal.The reason this approach was abandoned as the preferred embodiment wasthat there was an inherent gray area in the certainty of detecting thepresence or absence of the signal. By moving onward to a multitude ofbit planes, i.e. N>1, combined with simple pre-defined algorithmsprescribing the manner of choosing between a “0” and a “1”, theinvention moved the certainty question from the realm of expertstatistical analysis into the realm of guessing a random binary eventsuch as a coin flip. This is seen as a powerful feature relative to theintuitive acceptance of this invention in both the courtroom and themarketplace. The analogy which summarizes the inventor's thoughts onthis whole question is as follows: The search for a singleidentification signal amounts to calling a coin flip only once, andrelying on arcane experts to make the call; whereas the N>1 preferredembodiment of this invention relies on the broadly intuitive principleof correctly calling a coin flip N times in a row. This situation isgreatly exacerbated, i.e. the problems of “interpretation” of thepresence of a single signal, when images and sound clips get smaller andsmaller in extent.

[0091] Another important reason that the N>1 case is the preferredembodiment over the N=1 embodiment is that in the N=1 case, the mannerin which a suspect image is prepared and manipulated has a directbearing on the likelihood of making a positive identification. Thus, themanner with which an expert makes an identification determinationbecomes an integral part of that determination. The existence of amultitude of mathematical and statistical approaches to making thisdetermination leave open the possibility that some tests might makepositive identifications while others might make negativedeterminations, inviting further arcane debate about the relative meritsof the various identification approaches. The N>1 preferred embodimentof this invention avoids this further gray area by presenting a methodwhere no amount of preprocessing of a signal—other than preprocessingwhich surreptitiously uses knowledge of the private code signals—canincrease the likelihood of “calling the coin flip N times in a row.”

[0092] The fullest expression of the present system will come when itbecomes an industry standard and numerous independent groups set up withtheir own means or ‘in-house’ brand of applying embedded identificationnumbers and in their decipherment. Numerous independent groupidentification will further enhance the ultimate objectivity of themethod, thereby enhancing its appeal as an industry standard.

[0093] Use of True Polarity in Creating the Composite Embedded CodeSignal

[0094] The foregoing discussion made use of the 0 and 1 formalism ofbinary technology to accomplish its ends. Specifically, the 0's and 1'sof the N-bit identification word directly multiplied their correspondingindividual embedded code signal to form the composite embedded codesignal (step 8, FIG. 2). This approach certainly has its conceptualsimplicity, but the multiplication of an embedded code signal by 0 alongwith the storage of that embedded code contains a kind of inefficiency.

[0095] It is preferred to maintain the formalism of the 0 and 1 natureof the N-bit identification word, but to have the 0's of the word inducea subtraction of their corresponding embedded code signal. Thus, in step8 of FIG. 2, rather than only ‘adding’ the individual embedded codesignals which correspond to a ‘1’ in the N-bit identification word, wewill also ‘subtract’ the individual embedded code signals whichcorrespond to a ‘0’ in the N-bit identification word.

[0096] At first glance this seems to add more apparent noise to thefinal composite signal. But it also increases the energy-wise separationof the 0's from the 1's, and thus the ‘gain’ which is applied in step10, FIG. 2 can be correspondingly lower.

[0097] We can refer to this improvement as the use of true polarity. Themain advantage of this improvement can largely be summarized as‘informational efficiency.’

[0098] ‘Perceptual Orthogonality’ of the Individual Embedded CodeSignals

[0099] The foregoing discussion contemplates the use of generally randomnoise-like signals as the individual embedded code signals. This isperhaps the simplest form of signal to generate. However, there is aform of informational optimization which can be applied to the set ofthe individual embedded signals, which the applicant describes under therubric ‘perceptual orthogonality.’ This term is loosely based on themathematical concept of the orthogonality of vectors, with the currentadditional requirement that this orthogonality should maximize thesignal energy of the identification information while maintaining itbelow some perceptibility threshold. Put another way, the embedded codesignals need not necessarily be random in nature.

[0100] Use and Improvements of the First Embodiment in the Field ofEmulsion-Based Photography

[0101] The foregoing discussion outlined techniques that are applicableto photographic materials. The following section explores the details ofthis area further and discloses certain improvements which lendthemselves to a broad range of applications.

[0102] The first area to be discussed involves the pre-application orpre-exposing of a serial number onto traditional photographic products,such as negative film, print paper, transparencies, etc. In general,this is a way to embed a priori unique serial numbers (and byimplication, ownership and tracking information) into photographicmaterial. The serial numbers themselves would be a permanent part of thenormally exposed picture, as opposed to being relegated to the marginsor stamped on the back of a printed photograph, which all requireseparate locations and separate methods of copying. The ‘serial number’as it is called here is generally synonymous with the N-bitidentification word, only now we are using a more common industrialterminology.

[0103] In FIG. 2, step 11, the disclosure calls for the storage of the“original >image!” along with code images. Then in FIG. 3, step 9, itdirects that the original be subtracted from the suspect image, therebyleaving the possible identification codes plus whatever noise andcorruption has accumulated. Therefore, the previous disclosure made thetacit assumption that there exists an original without the compositeembedded signals.

[0104] Now in the case of selling print paper and other duplication filmproducts, this will still be the case, i.e., an “original” without theembedded codes will indeed exist and the basic methodology of the firstembodiment can be employed. The original film serves perfectly well asan ‘unencoded original.’

[0105] However, in the case where pre-exposed negative film is used, thecomposite embedded signal preexists on the original film and thus therewill never be an “original” separate from the pre-embedded signal. It isthis latter case, therefore, which will be examined a bit more closely,along with observations on how to best use the principles discussedabove (the former cases adhering to the previously outlined methods).

[0106] The clearest point of departure for the case of pre-numberednegative film, i.e. negative film which has had each and every framepre-exposed with a very faint and unique composite embedded signal,comes at step 9 of FIG. 3 as previously noted. There are certainly otherdifferences as well, but they are mostly logistical in nature, such ashow and when to embed the signals on the film, how to store the codenumbers and serial number, etc. Obviously the pre-exposing of film wouldinvolve a major change to the general mass production process ofcreating and packaging film.

[0107]FIG. 4 has a schematic outlining one potential post-hoc mechanismfor pre-exposing film. ‘Post-hoc’ refers to applying a process after thefull common manufacturing process of film has already taken place.Eventually, economies of scale may dictate placing this pre-exposingprocess directly into the chain of manufacturing film. Depicted in FIG.4 is what is commonly known as a film writing system. The computer, 106,displays the composite signal produced in step 8, FIG. 2, on itsphosphor screen. A given frame of film is then exposed by imaging thisphosphor screen, where the exposure level is generally very faint, i.e.generally imperceptible. Clearly, the marketplace will set its owndemands on how faint this should be, that is, the level of added‘graininess’ as practitioners would put it. Each frame of film issequentially exposed, where in general the composite image displayed onthe CRT 102 is changed for each and every frame, thereby giving eachframe of film a different serial number. The transfer lens 104highlights the focal conjugate planes of a film frame and the CRT face.

[0108] Getting back to the applying the principles of the foregoingembodiment in the case of pre-exposed negative film . . . At step 9,FIG. 3, if we were to subtract the “original” with its embedded code, wewould obviously be “erasing” the code as well since the code is anintegral part of the original. Fortunately, remedies do exist andidentifications can still be made. However, it will be a challenge toartisans who refine this embodiment to have the signal to noise ratio ofthe identification process in the pre-exposed negative case approach thesignal to noise ratio of the case where the un-encoded original exists.

[0109] A succinct definition of the problem is in order at this point.Given a suspect picture (signal), find the embedded identification codeIF a code exists at all. The problem reduces to one of finding theamplitude of each and every individual embedded code signal within thesuspect picture, not only within the context of noise and corruption aswas previously explained, but now also within the context of thecoupling between a captured image and the codes. ‘Coupling’ here refersto the idea that the captured image “randomly biases” thecross-correlation.

[0110] So, bearing in mind this additional item of signal coupling, theidentification process now estimates the signal amplitude of each andevery individual embedded code signal (as opposed to taking thecross-correlation result of step 12, FIG. 3). If our identificationsignal exists in the suspect picture, the amplitudes thus found willsplit into a polarity with positive amplitudes being assigned a ‘1’ andnegative amplitudes being assigned a ‘0’. Our unique identification codemanifests itself. If, on the other hand, no such identification codeexists or it is someone else's code, then a random gaussian-likedistribution of amplitudes is found with a random hash of values.

[0111] It remains to provide a few more details on how the amplitudes ofthe individual embedded codes are found. Again, fortunately, this exactproblem has been treated in other technological applications. Besides,throw this problem and a little food into a crowded room ofmathematicians and statisticians and surely a half dozen optimizedmethodologies will pop out after some reasonable period of time. It is arather cleanly defined problem.

[0112] One specific example solution comes from the field ofastronomical imaging. Here, it is a mature prior art to subtract out a“thermal noise frame” from a given CCD image of an object. Often,however, it is not precisely known what scaling factor to use insubtracting the thermal frame, and a search for the correct scalingfactor is performed. This is precisely the task of this step of thepresent embodiment.

[0113] General practice merely performs a common search algorithm on thescaling factor, where a scaling factor is chosen and a new image iscreated according to:

NEW IMAGE=ACQUIRED IMAGE−SCALE*THERMAL IMAGE   (4)

[0114] The new image is applied to the fast fourier transform routineand a scale factor is eventually found which minimizes the integratedhigh frequency content of the new image. This general type of searchoperation with its minimization of a particular quantity is exceedinglycommon. The scale factor thus found is the sought-for “amplitude.”Refinements which are contemplated but not yet implemented are where thecoupling of the higher derivatives of the acquired image and theembedded codes are estimated and removed from the calculated scalefactor. In other words, certain bias effects from the coupling mentionedearlier are present and should be eventually accounted for and removedboth through theoretical and empirical experimentation.

[0115] Use and Improvements in the Detection of Signal or ImageAlteration

[0116] Apart from the basic need of identifying a signal or image as awhole, there is also rather ubiquitous need to detect possiblealterations to a signal or image. The following section describes howthe foregoing embodiment, with certain modifications and improvements,can be used as a powerful tool in this area. The potential scenarios andapplications of detecting alterations are innumerable.

[0117] To first summarize, assume that we have a given signal or imagewhich has been positively identified using the basic methods outlinedabove. In other words, we know its N-bit identification word, itsindividual embedded code signals, and its composite embedded code. Wecan then fairly simply create a spatial map of the composite code'samplitude within our given signal or image. Furthermore, we can dividethis amplitude map by the known composite code's spatial amplitude,giving a normalized map, i.e. a map which should fluctuate about someglobal mean value. By simple examination of this map, we can visuallydetect any areas which have been significantly altered wherein the valueof the normalized amplitude dips below some statistically set thresholdbased purely on typical noise and corruption (error).

[0118] The details of implementing the creation of the amplitude maphave a variety of choices. One is to perform the same procedure which isused to determine the signal amplitude as described above, only now westep and repeat the multiplication of any given area of the signal imagewith a gaussian weight function centered about the area we areinvestigating.

[0119] Universal Versus Custom Codes

[0120] The disclosure thus far has outlined how each and every sourcesignal has its own unique set of individual embedded code signals. Thisentails the storage of a significant amount of additional codeinformation above and beyond the original, and many applications maymerit some form of economizing.

[0121] One such approach to economizing is to have a given set ofindividual embedded code signals be common to a batch of sourcematerials. For example, one thousand images can all utilize the samebasic set of individual embedded code signals. The storage requirementsof these codes then become a small fraction of the overall storagerequirements of the source material.

[0122] Furthermore, some applications can utilize a universal set ofindividual embedded code signals, i.e., codes which remain the same forall instances of distributed material. This type of requirement would beseen by systems which wish to hide the N-bit identification word itself,yet have standardized equipment be able to read that word. This can beused in systems which make go/no go decisions at point-of-readlocations. The potential drawback to this set-up is that the universalcodes are more prone to be sleuthed or stolen; therefore they will notbe as secure as the apparatus and methodology of the previouslydisclosed arrangement. Perhaps this is just the difference between ‘highsecurity’ and ‘air-tight security,’ a distinction carrying little weightwith the bulk of potential applications.

[0123] Use in Printing, Paper, Documents, Plastic Coated IdentificationCards, and Other Material Where Global Embedded Codes Can Be Imprinted

[0124] The term ‘signal’ is often used narrowly to refer to digital datainformation, audio signals, images, etc. A broader interpretation of‘signal,’ and the one more generally intended, includes any form ofmodulation of any material whatsoever. Thus, the micro-topology of apiece of common paper becomes a ‘signal’ (e.g. its height as a functionof x-y coordinates). The reflective properties of a flat piece ofplastic (as a function of space also) becomes a signal. The point isthat photographic emulsions, audio signals, and digitized informationare not the only types of signals capable of utilizing the principles ofthe present invention.

[0125] As a case in point, a machine very much resembling a brailleprinting machine can be designed so as to imprint unique ‘noise-like’indentations as outlined above. These indentations can be applied with apressure which is much smaller than is typically applied in creatingbraille, to the point where the patterns are not noticed by a normaluser of the paper. But by following the steps of the present disclosureand applying them via the mechanism of micro-indentations, a uniqueidentification code can be placed onto any given sheet of paper, be itintended for everyday stationary purposes, or be it for importantdocuments, legal tender, or other secured material.

[0126] The reading of the identification material in such an embodimentgenerally proceeds by merely reading the document optically at a varietyof angles. This would become an inexpensive method for deducing themicrotopology of the paper surface. Certainly other forms of reading thetopology of the paper are possible as well.

[0127] In the case of plastic encased material such as identificationcards, e.g. driver's licenses, a similar braille-like impressionsmachine can be utilized to imprint unique identification codes. Subtlelayers of photoreactive materials can also be embedded inside theplastic and ‘exposed.’

[0128] It is clear that wherever a material exists which is capable ofbeing modulated by ‘noise-like’ signals, that material is an appropriatecarrier for unique identification codes and utilization of theprinciples of the invention. All that remains is the matter ofeconomically applying the identification information and maintaining thesignal level below an acceptability threshold which each and everyapplication will define for itself.

[0129] Real Time Encoder

[0130] While the first class of embodiments most commonly employs astandard microprocessor or computer to perform the encodation of animage or signal, it is possible to utilize a custom encodation devicewhich may be faster than a typical Von Neuman-type processor. Such asystem can be utilized with all manner of serial data streams.

[0131] Music and videotape recordings are examples of serial datastreams—data streams which are often pirated. It would assistenforcement efforts if authorized recordings were encoded withidentification data so that pirated knock-offs could be traced to theoriginal from which they were made.

[0132] Piracy is but one concern driving the need for the presentinvention. Another is authentication. Often it is important to confirmthat a given set of data is really what it is purported to be (oftenseveral years after its generation).

[0133] To address these and other needs, the system 200 of FIG. 5 can beemployed. System 200 can be thought of as an identification coding blackbox 202. The system 200 receives an input signal (sometimes termed the“master” or “unencoded” signal) and a code word, and produces (generallyin real time) an identification-coded output signal. (Usually, thesystem provides key data for use in later decoding.) The contents of the“black box” 202 can take various forms. An exemplary black box system isshown in FIG. 6 and includes a look-up table 204, a digital noise source206, first and second scalers 208, 210, an adder/subtracter 212, amemory 214, and a register 216.

[0134] The input signal (which in the illustrated embodiment is an 8-20bit data signal provided at a rate of one million samples per second,but which in other embodiments could be an analog signal if appropriateA/D and D/A conversion is provided) is applied from an input 218 to theaddress input 220 of the look-up table 204. For each input sample (i.e.look-up table address), the table provides a corresponding 8-bit digitaloutput word. This output word is used as a scaling factor that isapplied to one input of the first scaler 208.

[0135] The first scaler 208 has a second input, to which is applied an8-bit digital noise signal from source 206. (In the illustratedembodiment, the noise source 206 comprises an analog noise source 222and an analog-to-digital converter 224 although, again, otherimplementations can be used.) The noise source in the illustratedembodiment has a zero mean output value, with a full width half maximum(FWHM) of 50-100 digital numbers (e.g. from −75 to +75).

[0136] The first scaler 208 multiplies the two 8-bit words at its inputs(scale factor and noise) to produce—for each sample of the system inputsignal—a 16-bit output word. Since the noise signal has a zero meanvalue, the output of the first scaler likewise has a zero mean value.

[0137] The output of the first scaler 208 is applied to the input of thesecond scaler 210. The second scaler serves a global scaling function,establishing the absolute magnitude of the identification signal thatwill ultimately be embedded into the input data signal. The scalingfactor is set through a scale control device 226 (which may take anumber of forms, from a simple rheostat to a graphically implementedcontrol in a graphical user interface), permitting this factor to bechanged in accordance with the requirements of different applications.The second scaler 210 provides on its output line 228 a scaled noisesignal. Each sample of this scaled noise signal is successively storedin the memory 214.

[0138] (In the illustrated embodiment, the output from the first scaler208 may range between −1500 and +1500 (decimal), while the output fromthe second scaler 210 is in the low single digits, (such as between −2and +2).) Register 216 stores a multi-bit identification code word. Inthe illustrated embodiment this code word consists of 8 bits, althoughlarger code words (up to hundreds of bits) are commonly used. These bitsare referenced, one at a time, to control how the input signal ismodulated with the scaled noise signal.

[0139] In particular, a pointer 230 is cycled sequentially through thebit positions of the code word in register 216 to provide a control bitof “0” or “1” to a control input 232 of the adder/subtracter 212. If,for a particular input signal sample, the control bit is a “1”, thescaled noise signal sample on line 232 is added to the input signalsample. If the control bit is a “0”, the scaled noise signal sample issubtracted from the input signal sample. The output 234 from theadder/subtracter 212 provides the black box's output signal.

[0140] The addition or subtraction of the scaled noise signal inaccordance with the bits of the code word effects a modulation of theinput signal that is generally imperceptible. However, with knowledge ofthe contents of the memory 214, a user can later decode the encoding,determining the code number used in the original encoding process.(Actually, use of memory 214 is optional, as explained below.)

[0141] It will be recognized that the encoded signal can be distributedin well known ways, including converted to printed image form, stored onmagnetic media (floppy diskette, analog or DAT tape, etc.), CD-ROM, etc.etc.

[0142] Decoding

[0143] A variety of techniques can be used to determine theidentification code with which a suspect signal has been encoded. Twoare discussed below. The first is less preferable than the latter formost applications, but is discussed herein so that the reader may have afuller context within which to understand the invention.

[0144] More particularly, the first decoding method is a differencemethod, relying on subtraction of corresponding samples of the originalsignal from the suspect signal to obtain difference samples, which arethen examined (typically individually) for deterministic coding indicia(i.e. the stored noise data). This approach may thus be termed a“sample-based, deterministic” decoding technique.

[0145] The second decoding method does not make use of the originalsignal. Nor does it examine particular samples looking for predeterminednoise characteristics. Rather, the statistics of the suspect signal (ora portion thereof) are considered in the aggregate and analyzed todiscern the presence of identification coding that permeates the entiresignal. The reference to permeation means the entire identification codecan be discerned from a small fragment of the suspect signal. Thislatter approach may thus be termed a “holographic, statistical” decodingtechnique.

[0146] Both of these methods begin by registering the suspect signal tomatch the original. This entails scaling (e.g. in amplitude, duration,color balance, etc.), and sampling (or resampling) to restore theoriginal sample rate. As in the earlier described embodiment, there area variety of well understood techniques by which the operationsassociated with this registration function can be performed.

[0147] As noted, the first decoding approach proceeds by subtracting theoriginal signal from the registered, suspect signal, leaving adifference signal. The polarity of successive difference signal samplescan then be compared with the polarities of the corresponding storednoise signal samples to determine the identification code. That is, ifthe polarity of the first difference signal sample matches that of thefirst noise signal sample, then the first bit of the identification codeis a 1. (In such case, the polarity of the 9th, 17th, 25th, etc. samplesshould also all be positive.) If the polarity of the first differencesignal sample is opposite that of the corresponding noise signal sample,then the first bit of the identification code is a 0.

[0148] By conducting the foregoing analysis with eight successivesamples of the difference signal, the sequence of bits that comprise theoriginal code word can be determined. If, as in the preferredembodiment, pointer 230 stepped through the code word one bit at a time,beginning with the first bit, during encoding, then the first 8 samplesof the difference signal can be analyzed to uniquely determine the valueof the 8-bit code word.

[0149] In a noise-free world (speaking here of noise independent of thatwith which the identification coding is effected), the foregoinganalysis would always yield the correct identification code. But aprocess that is only applicable in a noise-free world is of limitedutility indeed.

[0150] (Further, accurate identification of signals in noise-freecontexts can be handled in a variety of other, simpler ways: e.g.checksums; statistically improbable correspondence between suspect andoriginal signals; etc.) While noise-induced aberrations in decoding canbe dealt with—to some degree—by analyzing large portions of the signal,such aberrations still place a practical ceiling on the confidence ofthe process. Further, the villain that must be confronted is not alwaysas benign as random noise. Rather, it increasingly takes the form ofhuman-caused corruption, distortion, manipulation, etc. In such cases,the desired degree of identification confidence can only be achieved byother approaches.

[0151] The presently preferred approach (the “holographic, statistical”decoding technique) relies on recombining the suspect signal withcertain noise data (typically the data stored in memory 214), andanalyzing the entropy of the resulting signal. “Entropy” need not beunderstood in its most strict mathematical definition, it being merelythe most concise word to describe randomness (noise, smoothness,snowiness, etc.).

[0152] Most serial data signals are not random. That is, one sampleusually correlates—to some degree—with the adjacent samples. Noise, incontrast, typically is random. If a random signal (e.g. noise) is addedto (or subtracted from) a non-random signal, the entropy of theresulting signal generally increases. That is, the resulting signal hasmore random variations than the original signal. This is the case withthe encoded output signal produced by the present encoding process; ithas more entropy than the original, unencoded signal.

[0153] If, in contrast, the addition of a random signal to (orsubtraction from) a non-random signal reduces entropy, then somethingunusual is happening. It is this anomaly that the preferred decodingprocess uses to detect embedded identification coding.

[0154] To fully understand this entropy-based decoding method, it isfirst helpful to highlight a characteristic of the original encodingprocess: the similar treatment of every eighth sample.

[0155] In the encoding process discussed above, the pointer 230increments through the code word, one bit for each successive sample ofthe input signal. If the code word is eight bits in length, then thepointer returns to the same bit position in the code word every eighthsignal sample. If this bit is a “1”, noise is added to the input signal;if this bit is a “0”, noise is subtracted from the input signal. Due tothe cyclic progression of the pointer 230, every eighth sample of anencoded signal thus shares a characteristic: they are all eitheraugmented by the corresponding noise data (which may be negative), orthey are all diminished, depending on whether the bit of the code wordthen being addressed by pointer 230 is a “1” or a “0”.

[0156] To exploit this characteristic, the entropy-based decodingprocess treats every eighth sample of the suspect signal in likefashion. In particular, the process begins by adding to the 1st, 9th,17th, 25th, etc. samples of the suspect signal the corresponding scalednoise signal values stored in the memory 214 (i.e. those stored in the1st, 9th, 17th, 25th, etc., memory locations, respectively). The entropyof the resulting signal (i.e. the suspect signal with every 8th samplemodified) is then computed.

[0157] (Computation of a signal's entropy or randomness is wellunderstood by artisans in this field. One generally accepted techniqueis to take the derivative of the signal at each sample point, squarethese values, and then sum over the entire signal. However, a variety ofother well known techniques can alternatively be used.) The foregoingstep is then repeated, this time subtracting the stored noise valuesfrom the 1st, 9th, 17th, 25 etc. suspect signal samples.

[0158] One of these two operations will undo the encoding process andreduce the resulting signal's entropy; the other will aggravate it. Ifadding the noise data in memory 214 to the suspect signal reduces itsentropy, then this data must earlier have been subtracted from theoriginal signal. This indicates that pointer 230 was pointing to a “0”bit when these samples were encoded. (A “0” at the control input ofadder/subtracter 212 caused it to subtract the scaled noise from theinput signal.) Conversely, if subtracting the noise data from everyeighth sample of the suspect signal reduces its entropy, then theencoding process must have earlier added this noise. This indicates thatpointer 230 was pointing to a “1” bit when samples 1, 9, 17, 25, etc.,were encoded.

[0159] By noting whether entropy decreases by (a) adding or (b)subtracting the stored noise data to/from the suspect signal, it can bedetermined that the first bit of the code word is (a) a “0”, or (b) a“1”.

[0160] The foregoing operations are then conducted for the group ofspaced samples of the suspect signal beginning with the second sample(i.e. 2, 10, 18, 26 . . . ). The entropy of the resulting signalsindicate whether the second bit of the code word is a “0”. or a “1”.Likewise with the following 6 groups of spaced samples in the suspectsignal, until all 8 bits of the code word have been discerned.

[0161] It will be appreciated that the foregoing approach is notsensitive to corruption mechanisms that alter the values of individualsamples; instead, the process considers the entropy of the signal as awhole, yielding a high degree of confidence in the results. Further,even small excerpts of the signal can be analyzed in this manner,permitting piracy of even small details of an original work to bedetected. The results are thus statistically robust, both in the face ofnatural and human corruption of the suspect signal.

[0162] It will further be appreciated that the use of an N-bit code wordin this real time embodiment provides benefits analogous to thosediscussed above in connection with the batch encoding system. (Indeed,the present embodiment may be conceptualized as making use of Ndifferent noise signals, just as in the batch encoding system. The firstnoise signal is a signal having the same extent as the input signal, andcomprising the scaled noise signal at the 1st, 9th, 17th, 25th, etc.,samples (assuming N=8), with zeroes at the intervening samples. Thesecond noise signal is a similar one comprising the scaled noise signalat the 2d, 10th, 18th, 26th, etc., samples, with zeroes at theintervening samples. Etc. These signals are all combined to provide acomposite noise signal.) One of the important advantages inherent insuch a system is the high degree of statistical confidence (confidencewhich doubles with each successive bit of the identification code) thata match is really a match. The system does not rely on subjectiveevaluation of a suspect signal for a single, deterministic embedded codesignal.

[0163] Illustrative Variations

[0164] From the foregoing description, it will be recognized thatnumerous modifications can be made to the illustrated systems withoutchanging the fundamental principles. A few of these variations aredescribed below.

[0165] The above-described decoding process tries both adding andsubtracting stored noise data to/from the suspect signal in order tofind which operation reduces entropy. In other embodiments, only one ofthese operations needs to be conducted. For example, in one alternativedecoding process the stored noise data corresponding to every eighthsample of the suspect signal is only added to said samples. If theentropy of the resulting signal is thereby increased, then thecorresponding bit of the code word is a “1” (i.e. this noise was addedearlier, during the encoding process, so adding it again only compoundsthe signal's randomness). If the entropy of the resulting signal isthereby decreased, then the corresponding bit of the code word is a “0”.A further test of entropy if the stored noise samples are subtracted isnot required.

[0166] The statistical reliability of the identification process (codingand decoding) can be designed to exceed virtually any confidencethreshold (e.g. 99.9%, 99.99%, 99.999%, etc. confidence) by appropriateselection of the global scaling factors, etc. Additional confidence inany given application (unnecessary in most applications) can be achievedby rechecking the decoding process.

[0167] One way to recheck the decoding process is to remove the storednoise data from the suspect signal in accordance with the bits of thediscerned code word, yielding a “restored” signal (e.g. if the first bitof the code word is found to be “1,”then the noise samples stored in the1st, 9th, 17th, etc. locations of the memory 214 are subtracted from thecorresponding samples of the suspect signal). The entropy of therestored signal is measured and used as a baseline in furthermeasurements. Next, the process is repeated, this time removing thestored noise data from the suspect signal in accordance with a modifiedcode word. The modified code word is the same as the discerned codeword, except 1 bit is toggled (e.g. the first). The entropy of theresulting signal is determined, and compared with the baseline. If thetoggling of the bit in the discerned code word resulted in increasedentropy, then the accuracy of that bit of the discerned code word isconfirmed. The process repeats, each time with a different bit of thediscerned code word toggled, until all bits of the code word have beenso checked. Each change should result in an increase in entropy comparedto the baseline value.

[0168] The data stored in memory 214 is subject to a variety ofalternatives. In the foregoing discussion, memory 214 contains thescaled noise data. In other embodiments, the unscaled noise data can bestored instead.

[0169] In still other embodiments, it can be desirable to store at leastpart of the input signal itself in memory 214. For example, the memorycan allocate 8 signed bits to the noise sample, and 16 bits to store themost significant bits of an 18- or 20-bit audio signal sample. This hasseveral benefits. One is that it simplifies registration of a “suspect”signal. Another is that, in the case of encoding an input signal whichwas already encoded, the data in memory 214 can be used to discern whichof the encoding processes was performed first. That is, from the inputsignal data in memory 214 (albeit incomplete), it is generally possibleto determine with which of two code words it has been encoded.

[0170] Yet another alternative for memory 214 is that is can be omittedaltogether.

[0171] One way this can be achieved is to use a deterministic noisesource in the encoding process, such as an algorithmic noise generatorseeded with a known key number. The same deterministic noise source,seeded with the same key number, can be used in the decoding process. Insuch an arrangement, only the key number needs be stored for later usein decoding, instead of the large data set usually stored in memory 214.

[0172] Alternatively, if the noise signal added during encoding does nothave a zero mean value, and the length N of the code word is known tothe decoder, then a universal decoding process can be implemented. Thisprocess uses the same entropy test as the foregoing procedures, butcycles through possible code words, adding/subtracting a small dummynoise value (e.g. less than the expected mean noise value) to every Nthsample of the suspect signal, in accordance with the bits of the codeword being tested, until a reduction in entropy is noted. Such anapproach is not favored for most applications, however, because itoffers less security than the other embodiments (e.g. it is subject tocracking by brute force).

[0173] Many applications are well served by the embodiment illustratedin FIG. 7, in which different code words are used to produce severaldifferently encoded versions of an input signal, each making use of thesame noise data. More particularly, the embodiment 240 of FIG. 7includes a noise store 242 into which noise from source 206 is writtenduring the identification-coding of the input signal with a first codeword. (The noise source of FIG. 7 is shown outside of the real timeencoder 202 for convenience of illustration.) Thereafter, additionalidentification-coded versions of the input signal can be produced byreading the stored noise data from the store and using it in conjunctionwith second through Nth code words to encode the signal. (Whilebinary-sequential code words are illustrated in FIG. 7, in otherembodiments arbitrary sequences of code words can be employed.) Withsuch an arrangement, a great number of differently-encoded signals canbe produced, without requiring a proportionally-sized long term noisememory. Instead, a fixed amount of noise data is stored, whetherencoding an original once or a thousand times.

[0174] (If desired, several differently-coded output signals can beproduced at the same time, rather than seriatim. One such implementationincludes a plurality of adder/subtracter circuits 212, each driven withthe same input signal and with the same scaled noise signal, but withdifferent code words. Each, then, produces a differently encoded outputsignal.)

[0175] In applications having a great number of differently-encodedversions of the same original, it will be recognized that the decodingprocess need not always discern every bit of the code word. Sometimes,for example, the application may require identifying only a group ofcodes to which the suspect signal belongs. (E.g., high order bits of thecode word might indicate an organization to which several differentlycoded versions of the same source material were provided, with low-orderbits identifying specific copies. To identify the organization withwhich a suspect signal is associated, it may not be necessary to examinethe low order bits, since the organization can be identified by the highorder bits alone.) If the identification requirements can be met bydiscerning a subset of the code word bits in the suspect signal, thedecoding process can be shortened.

[0176] Some applications may be best served by restarting the encodingprocess—sometimes with a different code word—several times within anintegral work. Consider, as an example, videotaped productions (e.g.television programming). Each frame of a videotaped production can beidentification-coded with a unique code number, processed in real-timewith an arrangement 248 like that shown in FIG. 8. Each time a verticalretrace is detected by sync detector 250, the noise source 206 resets(e.g. to repeat the sequence just produced) and an identification codeincrements to the next value. Each frame of the videotape is therebyuniquely identification-coded. Typically, the encoded signal is storedon a videotape for long term storage (although other storage media,including laser disks, can be used).

[0177] Returning to the encoding apparatus, the look-up table 204 in theillustrated embodiment exploits the fact that high amplitude samples ofthe input data signal can tolerate (without objectionable degradation ofthe output signal) a higher level of encoded identification coding thancan low amplitude input samples. Thus, for example, input data sampleshaving decimal values of 0, 1 or 2 may correspond (in the look-up table204) to scale factors of unity (or even zero), whereas input datasamples having values in excess of 200 may correspond to scale factorsof 15. Generally speaking, the scale factors and the input sample valuescorrespond by a square root relation. That is, a four-fold increase in avalue of the sampled input signal corresponds to approximately atwo-fold increase in a value of the scaling factor associated therewith.

[0178] (The parenthetical reference to zero as a scaling factor alludesto cases, e.g., in which the source signal is temporally or spatiallydevoid of information content. In an image, for example, a regioncharacterized by several contiguous sample values of zero may correspondto a jet black region of the frame. A scaling value of zero may beappropriate here since there is essentially no image data to bepirated.)

[0179] Continuing with the encoding process, those skilled in the artwill recognized the potential for “rail errors” in the illustratedembodiment. For example, if the input signal consists of 8-bit samples,and the samples span the entire range from 0 to 255 (decimal), then theaddition or subtraction of scaled noise to/from the input signal mayproduce output signals that cannot be represented by 8 bits (e.g. −2, or257). A number of well-understood techniques exist to rectify thissituation, some of them proactive and some of them reactive. (Amongthese known techniques are: specifying that the input signal shall nothave samples in the range of 0-4 or 251-255, thereby safely permittingmodulation by the noise signal; or including provision for detecting andadaptively modifying input signal samples that would otherwise causerail errors.)

[0180] While the illustrated embodiment describes stepping through thecode word sequentially, one bit at a time, to control modulation ofsuccessive bits of the input signal, it will be appreciated that thebits of the code word can be used other than sequentially for thispurpose. Indeed, bits of the code word can be selected in accordancewith any predetermined algorithm.

[0181] The dynamic scaling of the noise signal based on theinstantaneous value of the input signal is an optimization that can beomitted in many embodiments. That is, the look-up table 204 and thefirst scaler 208 can be omitted entirely, and the signal from thedigital noise source 206 applied directly (or through the second, globalscaler 210) to the adder/subtracter 212.

[0182] It will be further recognized that the use of a zero-mean noisesource simplifies the illustrated embodiment, but is not necessary tothe invention. A noise signal with another mean value can readily beused, and D.C. compensation (if needed) can be effected elsewhere in thesystem.

[0183] The use of a noise source 206 is also optional. A variety ofother signal sources can be used, depending on application-dependentconstraints (e.g. the threshold at which the encoded identificationsignal becomes perceptible). In many instances, the level of theembedded identification signal is low enough that the identificationsignal needn't have a random aspect; it is imperceptible regardless ofits nature. A pseudo random source 206, however, is usually desiredbecause it provides the greatest identification code signal S/N ratio (asomewhat awkward term in this instance) for a level of imperceptibilityof the embedded identification signal.

[0184] It will be recognized that identification coding need not occurafter a signal has been reduced to stored form as data (i.e. “fixed intangible form,” in the words of the U.S. Copyright Act). Consider, forexample, the case of popular musicians whose performances are oftenrecorded illicitly. By identification coding the audio before it drivesconcert hall speakers, unauthorized recordings of the concert can betraced to a particular place and time. Likewise, live audio sources suchas 911 emergency calls can be encoded prior to recording so as tofacilitate their later authentication.

[0185] While the black box embodiment has been described as a standalone unit, it will be recognized that it can be integrated into anumber of different tools/instruments as a component. One is a scanner,which can embed identification codes in the scanned output data. (Thecodes can simply serve to memorialize that the data was generated by aparticular scanner). Another is in creativity software, such as populardrawing/graphics/animation/paint programs offered by Adobe, Macromedia,Corel, and the like.

[0186] Finally, while the real-time encoder 202 has been illustratedwith reference to a particular hardware implementation, it will berecognized that a variety of other implementations can alternatively beemployed. Some utilize other hardware configurations. Others make use ofsoftware routines for some or all of the illustrated functional blocks.(The software routines can be executed on any number of differentgeneral purpose programmable computers, such as 80×86 PC-compatiblecomputers, RISC-based workstations, etc.)

[0187] Types of Noise, Quasi-Noise, and Optimized Noise

[0188] Heretofore this disclosure postulated Gaussian noise, “whitenoise,” and noise generated directly from application instrumentation asa few of the many examples of the kind of carrier signal appropriate tocarry a single bit of information throughout an image or signal. It ispossible to be even more proactive in “designing” characteristics ofnoise in order to achieve certain goals. The “design” of using Gaussianor instrumental noise was aimed somewhat toward “absolute” security.This section of the disclosure takes a look at other considerations forthe design of the noise signals which may be considered the ultimatecarriers of the identification information.

[0189] For some applications it might be advantageous to design thenoise carrier signal (e.g. the Nth embedded code signal in the firstembodiment; the scaled noise data in the second embodiment), so as toprovide more absolute signal strength to the identification signalrelative to the perceptibility of that signal. One example is thefollowing. It is recognized that a true Gaussian noise signal has thevalue 0 occur most frequently, followed by 1 and −1 at equalprobabilities to each other but lower than 0, 2 and −2 next, and so on.Clearly, the value zero carries no information as it is used in theservice of this invention. Thus, one simple adjustment, or design, wouldbe that any time a zero occurs in the generation of the embedded codesignal, a new process takes over, whereby the value is converted“randomly” to either a 1 or a −1. In logical terms, a decision would bemade: if ‘0’, then random(1,−1). The histogram of such a process wouldappear as a Gaussian/Poissonian type distribution, except that the 0 binwould be empty and the 1 and −1 bin would be increased by half the usualhistogram value of the 0 bin.

[0190] In this case, identification signal energy would always beapplied at all parts of the signal. A few of the trade-offs include:there is a (probably negligible) lowering of security of the codes inthat a “deterministic component” is a part of generating the noisesignal. The reason this might be completely negligible is that we stillwind up with a coin flip type situation on randomly choosing the 1 orthe −1. Another trade-off is that this type of designed noise will havea higher threshold of perceptibility, and will only be applicable toapplications where the least significant bit of a data stream or imageis already negligible relative to the commercial value of the material,i.e. if the least significant bit were stripped from the signal (for allsignal samples), no one would know the difference and the value of thematerial would not suffer. This blocking of the zero value in theexample above is but one of many ways to “optimize” the noise propertiesof the signal carrier, as anyone in the art can realize. We refer tothis also as “quasi-noise” in the sense that natural noise can betransformed in a predetermined way into signals which for all intentsand purposes will read as noise. Also, cryptographic methods andalgorithms can easily, and often by definition, create signals which areperceived as completely random. Thus the word “noise” can have differentconnotations, primarily between that as defined subjectively by anobserver or listener, and that defined mathematically. The difference ofthe latter is that mathematical noise has different properties ofsecurity and the simplicity with which it can either be “sleuthed” orthe simplicity with which instruments can “automatically recognize” theexistence of this noise.

[0191] “Universal” Embedded Codes

[0192] The bulk of this disclosure teaches that for absolute security,the noise-like embedded code signals which carry the bits of informationof the identification signal should be unique to each and every encodedsignal, or, slightly less restrictive, that embedded code signals shouldbe generated sparingly, such as using the same embedded codes for abatch of 1000 pieces of film, for example. Be this as it may, there is awhole other approach to this issue wherein the use of what we will call“universal” embedded code signals can open up large new applications forthis technology. The economics of these uses would be such that the defacto lowered security of these universal codes (e.g. they would beanalyzable by time honored cryptographic decoding methods, and thuspotentially thwarted or reversed) would be economically negligiblerelative to the economic gains that the intended uses would provide.Piracy and illegitimate uses would become merely a predictable “cost”and a source of uncollected revenue only; a simple line item in aneconomic analysis of the whole. A good analogy of this is in the cableindustry and the scrambling of video signals. Everybody seems to knowthat crafty, skilled technical individuals, who may be generally lawabiding citizens, can climb a ladder and flip a few wires in their cablejunction box in order to get all the pay channels for free. The cableindustry knows this and takes active measures to stop it and prosecutethose caught, but the “lost revenue” derived from this practice remainsprevalent but almost negligible as a percentage of profits gained fromthe scrambling system as a whole. The scrambling system as a whole is aneconomic success despite its lack of “absolute security.”

[0193] The same holds true for applications of this technology wherein,for the price of lowering security by some amount, large economicopportunity presents itself This section first describes what is meantby universal codes, then moves on to some of the interesting uses towhich these codes can be applied.

[0194] Universal embedded codes generally refer to the idea thatknowledge of the exact codes can be distributed. The embedded codeswon't be put into a dark safe never to be touched until litigationarises (as alluded to in other parts of this disclosure), but insteadwill be distributed to various locations where on-the-spot analysis cantake place. Generally this distribution will still take place within asecurity controlled environment, meaning that steps will be taken tolimit the knowledge of the codes to those with a need to know.Instrumentation which attempts to automatically detect copyrightedmaterial is a non-human example of “something” with a need to know thecodes.

[0195] There are many ways to implement the idea of universal codes,each with their own merits regarding any given application. For thepurposes of teaching this art, we separate these approaches into threebroad categories: universal codes based on libraries, universal codesbased on deterministic formula, and universal codes based on pre-definedindustry standard patterns. A rough rule of thumb is that the first ismore secure than the latter two, but that the latter two are possiblymore economical to implement than the first.

[0196] Universal Codes: 1) Libraries of Universal Codes

[0197] The use of libraries of universal codes simply means that thetechniques of this invention are employed as described, except for thefact that only a limited set of the individual embedded code signals aregenerated and that any given encoded material will make use of somesub-set of this limited “universal set.” An example is in order here. Aphotographic print paper manufacturer may wish to preexpose every pieceof 8 by 10 inch print paper which they sell with a unique identificationcode. They also wish to sell identification code recognition software totheir large customers, service bureaus, stock agencies, and individualphotographers, so that all these people can not only verify that theirown material is correctly marked, but so that they can also determine ifthird party material which they are about to acquire has been identifiedby this technology as being copyrighted. This latter information willhelp them verify copyright holders and avoid litigation, among manyother benefits. In order to “economically” institute this plan, theyrealize that generating unique individual embedded codes for each andevery piece of print paper would generate Terabytes of independentinformation, which would need storing and to which recognition softwarewould need access. Instead, they decide to embed their print paper with16 bit identification codes derived from a set of only 50 independent“universal” embedded code signals. The details of how this is done arein the next paragraph, but the point is that now their recognitionsoftware only needs to contain a limited set of embedded codes in theirlibrary of codes, typically on the order of 1 Megabyte to 10 Megabytesof information for 50×16 individual embedded codes splayed out onto an8×10 photographic print (allowing for digital compression). The reasonfor picking 50 instead of just 16 is one of a little more addedsecurity, where if it were the same 16 embedded codes for allphotographic sheets, not only would the serial number capability belimited to 2 to the 16th power, but lesser and lesser sophisticatedpirates could crack the codes and remove them using software tools.

[0198] There are many different ways to implement this scheme, where thefollowing is but one exemplary method. It is determined by the wisdom ofcompany management that a 300 pixels per inch criteria for the embeddedcode signals is sufficient resolution for most applications. This meansthat a composite embedded code image will contain 3000 pixels by 2400pixels to be exposed at a very low level onto each 8×10 sheet. Thisgives 7.2 million pixels. Using our staggered coding system such asdescribed in the black box implementation of FIGS. 5 and 6, eachindividual embedded code signal will contain only 7.2 million divided by16, or approximately 450K true information carrying pixels, i.e. every16th pixel along a given raster line. These values will typically be inthe range of 2 to −2 in digital numbers, or adequately described by asigned 3 bit number. The raw information content of an embedded code isthen approximately ⅜th's bytes times 450K or about 170 Kilobytes.Digital compression can reduce this further. All of these decisions aresubject to standard engineering optimization principles as defined byany given application at hand, as is well known in the art. Thus we findthat 50 of these independent embedded codes will amount to a fewMegabytes. This is a quite reasonable level to distribute as a “library”of universal codes within the recognition software. Advanced standardencryption devices could be employed to mask the exact nature of thesecodes if one were concerned that would-be pirates would buy therecognition software merely to reverse engineer the universal embeddedcodes. The recognition software could simply unencrypt the codes priorto applying the recognition techniques taught in this disclosure.

[0199] The recognition software itself would certainly have a variety offeatures, but the core task it would perform is determining if there issome universal copyright code within a given image. The key questionsbecome WHICH 16 of the total 50 universal codes it might contain, ifany, and if there are 16 found, what are their bit values. The keyvariables in determining the answers to these questions are:registration, rotation, magnification (scale), and extent. In the mostgeneral case with no helpful hints whatsoever, all variables must beindependently varied across all mutual combinations, and each of the 50universal codes must then be checked by adding and subtracting to see ifan entropy decrease occurs. Strictly speaking, this is an enormous job,but many helpful hints will be found which make the job much simpler,such as having an original image to compare to the suspected copy, orknowing the general orientation and extent of the image relative to an8×10 print paper, which then through simple registration techniques candetermine all of the variables to some acceptable degree. Then it merelyrequires cycling through the 50 universal codes to find any decrease inentropy. If one does, then 15 others should as well. A protocol needs tobe set up whereby a given order of the 50 translates into a sequence ofmost significant bit through least significant bit of the ID code word.Thus if we find that universal code number “4” is present, and we findits bit value to be “0”, and that universal codes “1” through “3” aredefinitely not present, then our most significant bit of our N-bit IDcode number is a “0”. Likewise, we find that the next lowest universalcode present is number “7” and it turns out to be a “1”, then our nextmost significant bit is a “1”. Done properly, this system can cleanlytrace back to the copyright owner so long as they registered theirphotographic paper stock serial number with some registry or with themanufacturer of the paper itself. That is, we look up in the registrythat a paper using universal embedded codes 4, 7, 11, 12, 15, 19, 21,26, 27, 28, 34, 35, 37, 38, 40, and 48, and having the embedded code0110 0101 0111 0100 belongs to Leonardo de Boticelli, an unknownwildlife photographer and glacier cinematographer whose address is inNorthern Canada. We know this because he dutifully registered his filmand paper stock, a few minutes of work when he bought the stock, whichhe plopped into the “no postage necessary” envelope that themanufacturing company kindly provided to make the process ridiculouslysimple. Somebody owes Leonardo a royalty check it would appear, andcertainly the registry has automated this royalty payment process aspart of its services.

[0200] One final point is that truly sophisticated pirates and otherswith illicit intentions can indeed employ a variety of cryptographic andnot so cryptographic methods to crack these universal codes, sell them,and make software and hardware tools which can assist in the removing ordistorting of codes. We shall not teach these methods as part of thisdisclosure, however. In any event, this is one of the prices which mustbe paid for the ease of universal codes and the applications they openup.

[0201] Universal Codes: 2) Universal Codes Based on DeterministicFormulas

[0202] The libraries of universal codes require the storage andtransmittal of Megabytes of independent, generally random data as thekeys with which to unlock the existence and identity of signals andimagery that have been marked with universal codes. Alternatively,various deterministic formulas can be used which “generate” what appearto be random data/image frames, thereby obviating the need to store allof these codes in memory and interrogate each and every of the “50”universal codes. Deterministic formulas can also assist in speeding upthe process of determining the ID code once one is known to exist in agiven signal or image. On the other hand, deterministic formulas lendthemselves to sleuthing by less sophisticated pirates. And oncesleuthed, they lend themselves to easier communication, such as postingon the Internet to a hundred newsgroups. There may well be manyapplications which do not care about sleuthing and publishing, anddeterministic formulas for generating the individual universal embeddedcodes might be just the ticket.

[0203] Universal Codes: 3) “Simple” Universal Codes

[0204] This category is a bit of a hybrid of the first two, and is mostdirected at truly large scale implementations of the principles of thistechnology. The applications employing this class are of the type wherestaunch security is much less important than low cost, large scaleimplementation and the vastly larger economic benefits that thisenables. One exemplary application is placement of identificationrecognition units directly within modestly priced home audio and videoinstrumentation (such as a TV). Such recognition units would typicallymonitor audio and/or video looking for these copyright identificationcodes, and thence triggering simple decisions based on the findings,such as disabling or enabling recording capabilities, or incrementingprogram specific billing meters which are transmitted back to a centralaudio/video service provider and placed onto monthly invoices. Likewise,it can be foreseen that “black boxes” in bars and other public placescan monitor (listen with a microphone) for copyrighted materials andgenerate detailed reports, for use by ASCAP, BMI, and the like.

[0205] A core principle of simple universal codes is that some basicindustry standard “noiselike” and seamlessly repetitive patterns areinjected into signals, images, and image sequences so that inexpensiverecognition units can either A) determine the mere existence of acopyright “flag”, and B) additionally to A, determine preciseidentification information which can facilitate more complex decisionmaking and actions.

[0206] In order to implement this particular embodiment of the presentinvention, the basic principles of generating the individual embeddednoise signals need to be simplified in order to accommodate inexpensiverecognition signal processing circuitry, while maintaining theproperties of effective randomness and holographic permeation. Withlarge scale industry adoption of these simple codes, the codesthemselves would border on public domain information (much as cablescrambling boxes are almost de facto public domain), leaving the dooropen for determined pirates to develop black market countermeasures, butthis situation would be quite analogous to the scrambling of cable videoand the objective economic analysis of such illegal activity.

[0207] One prior art known to the applicant in this general area ofpro-active copyright detection is the Serial Copy Management Systemadopted by many firms in the audio industry. To the best of applicant'sknowledge, this system employs a non-audio “flag” signal which is notpart of the audio data stream, but which is nevertheless grafted ontothe audio stream and can indicate whether the associated audio datashould or should not be duplicated. One problem with this system is thatit is restricted to media and instrumentation which can support thisextra “flag” signal. Another deficiency is that the flagging systemcarries no identity information which would be useful in making morecomplex decisions. Yet another difficulty is that high quality audiosampling of an analog signal can come arbitrarily close to making aperfect digital copy of some digital master and there seems to be noprovision for inhibiting this possibility.

[0208] The principles of this invention can be brought to bear on theseand other problems, in audio applications, video, and all of the otherapplications previously discussed. An exemplary application of simpleuniversal codes is the following. A single industry standard “1.000000second of noise” would be defined as the most basic indicator of thepresence or absence of the copyright marking of any given audio signal.FIG. 9 has an example of what the waveform of an industry standard noisesecond might look like, both in the time domain 400 and the frequencydomain 402. It is by definition a continuous function and would adapt toany combination of sampling rates and bit quanitizations. It has anormalized amplitude and can be scaled arbitrarily to any digital signalamplitude. The signal level and the first M'th derivatives of the signalare continuous at the two boundaries 404 (FIG. 9C), such that when it isrepeated, the “break” in the signal would not be visible (as a waveform)or audible when played through a high end audio system. The choice of 1second is arbitrary in this example, where the precise length of theinterval will be derived from considerations such as audibility,quasi-white noise status, seamless repeatability, simplicity ofrecognition processing, and speed with which a copyright markingdetermination can be made. The injection of this repeated noise signalonto a signal or image (again, at levels below human perception) wouldindicate the presence of copyright material. This is essentially a onebit identification code, and the embedding of further identificationinformation will be discussed later on in this section. The use of thisidentification technique can extend far beyond the low cost homeimplementations discussed here, where studios could use the technique,and monitoring stations could be set up which literally monitor hundredsof channels of information simultaneously, searching for marked datastreams, and furthermore searching for the associated identity codeswhich could be tied in with billing networks and royalty trackingsystems.

[0209] This basic, standardized noise signature is seamlessly repeatedover and over again and added to audio signals which are to be markedwith the base copyright identification. Part of the reason for the word“simple” is seen here: clearly pirates will know about this industrystandard signal, but their illicit uses derived from this knowledge,such as erasure or corruption, will be economically minuscule relativeto the economic value of the overall technique to the mass market. Formost high end audio this signal will be some 80 to 100 dB down from fullscale, or even much further; each situation can choose its own levelsthough certainly there will be recommendations. The amplitude of thesignal can be modulated according to the audio signal levels to whichthe noise signature is being applied, i.e. the amplitude can increasesignificantly when a drum beats, but not so dramatically as to becomeaudible or objectionable. These measures merely assist the recognitioncircuitry to be described.

[0210] Recognition of the presence of this noise signature by low costinstrumentation can be effected in a variety of ways. One rests on basicmodifications to the simple principles of audio signal power metering.Software recognition programs can also be written, and moresophisticated mathematical detection algorithms can be applied to audioin order to make higher confidence detection identifications. In suchembodiments, detection of the copyright noise signature involvescomparing the time averaged power level of an audio signal with the timeaveraged power level of that same audio signal which has had the noisesignature subtracted from it. If the audio signal with the noisesignature subtracted has a lower power level that the unchanged audiosignal, then the copyright signature is present and some status flag tothat effect needs to be set. The main engineering subtleties involved inmaking this comparison include: dealing with audio speed playbackdiscrepancies (e.g. an instrument might be 0.5% “slow” relative toexactly one second intervals); and, dealing with the unknown phase ofthe one second noise signature within any given audio (basically, its“phase” can be anywhere from 0 to 1 seconds). Another subtlety, not socentral as the above two but which nonetheless should be addressed, isthat the recognition circuits should not subtract a higher amplitude ofthe noise signature than was originally embedded onto the audio signal.Fortunately this can be accomplished by merely subtracting only a smallamplitude of the noise signal, and if the power level goes down, this isan indication of “heading toward a trough” in the power levels. Yetanother related subtlety is that the power level changes will be verysmall relative to the overall power levels, and calculations generallywill need to be done with appropriate bit precision, e.g. 32 bit valueoperations and accumulations on 16-20 bit audio in the calculations oftime averaged power levels.

[0211] Clearly, designing and packaging this power level comparisonprocessing circuitry for low cost applications is an engineeringoptimization task. One trade-off will be the accuracy of making anidentification relative to the “short-cuts” which can be made to thecircuitry in order to lower its cost and complexity. A preferredembodiment for the placement of this recognition circuitry inside ofinstrumentation is through a single programmable integrated circuitwhich is custom made for the task. FIG. 10 shows one such integratedcircuit 506. Here the audio signal comes in, 500, either as a digitalsignal or as an analog signal to be digitized inside the IC 500, and theoutput is a flag 502 which is set to one level if the copyright noisesignature is found, and to another level if it is not found. Alsodepicted is the fact that the standardized noise signature waveform isstored in Read Only Memory, 504, inside the IC 506. There will be aslight time delay between the application of an audio signal to the IC506 and the output of a valid flag 502, due to the need to monitor somefinite portion of the audio before a recognition can take place. In thiscase, there may need to be a “flag valid” output 508 where the ICinforms the external world if it has had enough time to make a properdetermination of the presence or absence of the copyright noisesignature.

[0212] There are a wide variety of specific designs and philosophies ofdesigns applied to accomplishing the basic function of the IC 506 ofFIG. 10. Audio engineers and digital signal processing engineers areable to generate several fundamentally different designs. One suchdesign is depicted in FIG. 11 by a process 599, which itself is subjectto further engineering optimization as will be discussed. FIG. 11depicts a flow chart for any of: an analog signal processing network, adigital signal processing network, or programming steps in a softwareprogram. We find an input signal 600 which along one path is applied toa time averaged power meter 602, and the resulting power output itselftreated as a signal P_(sig). To the upper right we find the standardnoise signature 504 which will be read out at 125% of normal speed, 604,thus changing its pitch, giving the “pitch changed noise signal” 606.Then the input signal has this pitch changed noise signal subtracted instep 608, and this new signal is applied to the same form of timeaveraged power meter as in 602, here labelled 610. The output of thisoperation is also a time based signal here labelled as P_(S-PCN) 610.Step 612 then subtracts the power signal 602 from the power signal 610,giving an output difference signal P_(out) 613. If the universalstandard noise signature does indeed exist on the input audio signal600, then case 2, 616, will be created wherein a beat signal 618 ofapproximately 4 second period will show up on the output signal 613, andit remains to detect this, beat signal with a step such as in FIG. 12,622. Case 1, 614, is a steady noisy signal which exhibits no periodicbeating. 125% at step 604 is chosen arbitrarily here, where engineeringconsiderations would determine an optimal value, leading to differentbeat signal frequencies 618. Whereas waiting 4 seconds in this examplewould be quite a while, especially if you would want to detect at leasttwo or three beats, FIG. 12 outlines how the basic design of FIG. 11could be repeated and operated upon various delayed versions of theinput signal, delayed by something like {fraction (1/20)}th of a second,with 20 parallel circuits working in concert each on a segment of theaudio delayed by 0.05 seconds from their neighbors. In this way, a beatsignal will show up approximately every ⅕th of a second and will looklike a travelling wave down the columns of beat detection circuits. Theexistence or absence of this travelling beat wave triggers the detectionflag 502. Meanwhile, there would be an audio signal monitor 624 whichwould ensure that, for example, at least two seconds of audio has beenheard before setting the flag valid signal 508.

[0213] Though the audio example was described above, it should be clearto anyone in the art that the same type of definition of some repetitiveuniversal noise signal or image could be applied to the many othersignals, images, pictures, and physical media already discussed.

[0214] The above case deals only with a single bit plane of information,i.e., the noise signature signal is either there (1) or it isn't (0).For many applications, it would be nice to detect serial numberinformation as well, which could then be used for more complexdecisions, or for logging information on billing statements or whatnot.The same principles as the above would apply, but now there would be Nindependent noise signatures as depicted in FIG. 9 instead of one singlesuch signature. Typically, one such signature would be the master uponwhich the mere existence of a copyright marking is detected, and thiswould have generally higher power than the others, and then the otherlower power “identification” noise signatures would be embedded intoaudio. Recognition circuits, once having found the existence of theprimary noise signature, would then step through the other N noisesignatures applying the same steps as described above. Where a beatsignal is detected, this indicates the bit value of ‘1’, and where nobeat signal is detected, this indicates a bit value of ‘0’. It might betypical that N will equal 32, that way 2.sup.32 number of identificationcodes are available to any given industry employing this invention.

[0215] Use of this Technology When the Length of the Identification Codeis 1

[0216] The principles of this invention can obviously be applied in thecase where only a single presence or absence of an identificationsignal—a fingerprint if you will—is used to provide confidence that somesignal or image is copyrighted. The example above of the industrystandard noise signature is one case in point. We no longer have theadded confidence of the coin flip analogy, we no longer have trackingcode capabilities or basic serial number capabilities, but manyapplications may not require these attributes and the added simplicityof a single fingerprint might outweigh these other attributes in anyevent.

[0217] The “Wallpaper” Analogy

[0218] The term “holographic” has been used in this disclosure todescribe how an identification code number is distributed in a largelyintegral form throughout an encoded signal or image. This also refers tothe idea that any given fragment of the signal or image contains theentire unique identification code number. As with physicalimplementations of holography, there are limitations on how small afragment can become before one begins to lose this property, where theresolution limits of the holographic media are the main factor in thisregard for holography itself In the case of an uncorrupted distributionsignal which has used the encoding device of FIG. 5, and whichfurthermore has used our “designed noise” of above wherein the zero'swere randomly changed to a 1 or −1, then the extent of the fragmentrequired is merely N contiguous samples in a signal or image rasterline, where N is as defined previously being the length of ouridentification code number. This is an informational extreme; practicalsituations where noise and corruption are operative will requiregenerally one, two or higher orders of magnitude more samples than thissimple number N. Those skilled in the art will recognize that there aremany variables involved in pinning down precise statistics on the sizeof the smallest fragment with which an identification can be made.

[0219] For tutorial purposes, the applicant also uses the analogy thatthe unique identification code number is “wallpapered” across an image(or signal). That is, it is repeated over and over again all throughoutan image. This repetition of the ID code number can be regular, as inthe use of the encoder of FIG. 5, or random itself, where the bits inthe ID code 216 of FIG. 6 are not stepped through in a normal repetitivefashion but rather are randomly selected on each sample, and the randomselection stored along with the value of the output 228 itself. In anyevent, the information carrier of the ID code, the individual embeddedcode signal, does change across the image or signal. Thus as thewallpaper analogy summarizes: the ID code repeats itself over and over,but the patterns that each repetition imprints change randomlyaccordingly to a generally unsleuthable key.

[0220] Lossy Data Compression

[0221] As earlier mentioned, the identification coding of the preferredembodiment withstands lossy data compression, and subsequentdecompression. Such compression is finding increasing use, particularlyin contexts such as the mass distribution of digitized entertainmentprogramming (movies, etc.).

[0222] While data encoded according to the preferred embodiment of thepresent invention can withstand all types of lossy compression known toapplicant, those expected to be most commercially important are theCCITT G3, CCITT G4, JPEG, MPEG and JBIG compression/decompressionstandards. The CCITT standards are widely used in black-and-whitedocument compression (e.g. facsimile and document-storage). JPEG is mostwidely used with still images. MPEG is most widely used with movingimages. JBIG is a likely successor to the CCITT standards for use withblack-and-white imagery. Such techniques are well known to those in thelossy data compression field; a good overview can be found in Pennebakeret al, JPEG, Still Image Data Compression Standard, Van NostrandReinhold, N.Y., 1993.

[0223] Towards Steganography Proper and the Use of this Technology inPassing More Complex Messages or Information

[0224] This disclosure concentrates on what above was calledwallpapering a single identification code across an entire signal. Thisappears to be a desirable feature for many applications. However, thereare other applications where it might be desirable to pass messages orto embed very long strings of pertinent identification information insignals and images. One of many such possible applications would bewhere a given signal or image is meant to be manipulated by severaldifferent groups, and that certain regions of an image are reserved foreach group's identification and insertion of pertinent manipulationinformation.

[0225] In these cases, the code word 216 in FIG. 6 can actually changein some pre-defined manner as a function of signal or image position.For example, in an image, the code could change for each and everyraster line of the digital image. It might be a 16 bit code word, 216,but each scan line would have a new code word, and thus a 480 scan lineimage could pass a 980 (480×2 bytes) byte message. A receiver of themessage would need to have access to either the noise signal stored inmemory 214, or would have to know the universal code structure of thenoise codes if that method of coding was being used. To the best ofapplicant's knowledge, this is a novel approach to the mature field ofsteganography.

[0226] In all three of the foregoing applications of universal codes, itwill often be desirable to append a short (perhaps 8- or 16-bit) privatecode, which users would keep in their own secured places, in addition tothe universal code. This affords the user a farther modicum of securityagainst potential erasure of the universal codes by sophisticatedpirates.

[0227] One Master Code Signal As A Distinction From N IndependentEmbedded Code Signals

[0228] In certain sections of this disclosure, perhaps exemplified inthe section on the realtime encoder, an economizing step was takenwhereby the N independent and source-signal-coextensive embedded codesignals were so designed that the non-zero elements of any givenembedded code signal were unique to just that embedded code signal andno others. Said more carefully, certain pixels/sample points of a givensignal were “assigned” to some pre-determined m'th bit location in ourN-bit identification word. Furthermore, and as another basicoptimization of implementation, the aggregate of these assignedpixels/samples across all N embedded code signals is precisely theextent of the source signal, meaning each and every pixel/samplelocation in a source signal is assigned one and only one m'th bit placein our N-bit identification word. (This is not to say, however, thateach and every pixel MUST be modified). As a matter of simplification wecan then talk about a single master code signal (or “Snowy Image”)rather than N independent signals, realizing that pre-defined locationsin this master signal correspond to unique bit locations in our N-bitidentification word. We therefore construct, via this circuitous route,this rather simple concept on the single master noise signal. Beyondmere economization and simplification, there are also performancereasons for this shift, primarily derived from the idea that individualbit places in our N-bit identification word are no longer “competing”for the information carrying capacity of a single pixel/sample.

[0229] With this single master more clearly understood, we can gain newinsights into other sections of this disclosure and explore furtherdetails within the given application areas.

[0230] More of Deterministic Universal Codes Using the Master CodeConcept

[0231] One case in point is to further explore the use of DeterministicUniversal Codes, labelled as item “2” in the sections devoted touniversal codes. A given user of this technology may opt for thefollowing variant use of the principles of this invention. The user inquestion might be a mass distributor of home videos, but clearly theprinciples would extend to all other potential users of this invention.FIG. 13 pictorially represents the steps involved. In the example theuser is one “Alien Productions.” They first create an image canvas whichis coextensive to the size of the video frames of their movie “Bud'sAdventures.” On this canvas they print the name of the movie, they placetheir logo and company name. Furthermore, they have specific informationat the bottom, such as the distribution lot for the mass copying thatthey are currently cranking out, and as indicated, they actually have aunique frame number indicated. Thus we find the example of a standardimage 700 which forms the initial basis for the creation of a masterSnowy Image (master code signal) which will be added into the originalmovie frame, creating an output distributable frame. This image 700 canbe either black & white or color. The process of turning this image 700into a pseudo random master code signal is alluded to by theencryption/scrambling routine 702, wherein the original image 700 ispassed through any of dozens of well known scrambling methods. Thedepiction of the number “28” alludes to the idea that there can actuallybe a library of scrambling methods, and the particular method used forthis particular movie, or even for this particular frame, can change.The result is our classic master code signal or Snowy Image. In general,its brightness values are large and it would look very much like thesnowy image on a television set tuned to a blank channel, but clearly ithas been derived from an informative image 700, transformed through ascrambling 702. (Note: the splotchiness of the example picture isactually a rather poor depiction; it was a function of the crude toolsavailable to the inventor).

[0232] This Master Snowy Image 704 is then the signal which is modulatedby our N-bit identification word as outlined in other sections of thedisclosure, the resulting modulated signal is then scaled down inbrightness to the acceptable perceived noise level, and then added tothe original frame to produce the distributable frame.

[0233] There are a variety of advantages and features that the methoddepicted in FIG. 13 affords. There are also variations of theme withinthis overall variation. Clearly, one advantage is that users can now usemore intuitive and personalized methods for stamping and signing theirwork. Provided that the encryption/scrambling routines, 702, are indeedof a high security and not published or leaked, then even if a would-bepirate has knowledge of the logo image 700, they should not be able touse this knowledge to be able to sleuth the Master Snowy Image 704, andthus they should not be able to crack the system, as it were. On theother hand, simple encryption routines 702 may open the door forcracking the system. Another clear advantage of the method of FIG. 13 isthe ability to place further information into the overall protectiveprocess. Strictly speaking, the information contained in the logo image700 is not directly carried in the final distributable frame. Saidanother way, and provided that the encryption/scrambling routine 702 hasa straightforward and known decryption/descrambling method whichtolerates bit truncation errors, it is generally impossible to fullyre-create the image 700 based upon having the distributable frame, theN-bit identification code word, the brightness scaling factor used, andthe number of the decryption routine to be used. The reason that anexact recreation of the image 700 is impossible is due to the scalingoperation itself and the concomitant bit truncation. For the presentdiscussion, this whole issue is somewhat academic, however.

[0234] A variation on the theme of FIG. 13 is to actually place theN-bit identification code word directly into the logo image 700. In somesense this would be self-referential. Thus when we pull out our storedlogo image 700 it already contains visually what our identification wordis, then we apply encryption routine #28 to this image, scale it down,then use this version to decode a suspect image using the techniques ofthis disclosure. The N bit word thus found should match the onecontained in our logo image 700.

[0235] One desirable feature of the encryption/scrambling routine 702might be (but is certainly not required to be) that even given a smallchange in the input image 700, such as a single digit change of theframe number, there would be a huge visual change in the outputscrambled master snowy image 704. Likewise, the actual scramblingroutine may change as a function of frame numbers, or certain “seed”numbers typically used within pseudo-randomizing functions could changeas a function of frame number. All manner of variations are thuspossible, all helping to maintain high levels of security. Eventually,engineering optimization considerations will begin to investigate therelationship between some of these randomizing methods, and how they allrelate to maintaining acceptable signal strength levels through theprocess of transforming an uncompressed video stream into a compressedvideo stream such as with the MPEG compression methodologies.

[0236] Another desired feature of the encryption process 702 is that itshould be informationally efficient, i.e., that given any random input,it should be able to output an essentially spatially uniform noisy imagewith little to no residual spatial patterns beyond pure randomness. Anyresidual correlated patterns will contribute to inefficiency of encodingthe N-bit identification word, as well as opening up further tools towould-be pirates to break the system.

[0237] Another feature of the method of FIG. 13 is that there is moreintuitional appeal to using recognizable symbols as part of a decodingsystem, which should then translate favorably in the essentially layenvironment of a courtroom. It strengthens the simplicity of the coinflip vernacular mentioned elsewhere. Jury members or judges will betterrelate to an owner's logo as being a piece of the key of recognizing asuspect copy as being a knock-off.

[0238] It should also be mentioned that, strictly speaking, the logoimage 700 does not need to be randomized. The steps of the inventioncould equally apply straight to the logo image 700 directly. It is notentirely clear to the inventor what practical goal this might have. Atrivial extension of this concept to the case where N=1 is where, simplyand easily, the logo image 700 is merely added to an original image at avery low brightness level. The inventor does not presume this trivialcase to be at all a novelty. In many ways this is similar to the age oldissue of subliminal advertising, where the low light level patternsadded to an image are recognizable to the human eye/brain systemand—supposedly—operating on the human brain at an unconscious level. Bypointing out these trivial extensions of the current invention.Hopefully there can arise further clarity which distinguishes the novelprinciples of this invention in relation to such well known prior arttechniques.

[0239] 5-bit Abridged Alphanumeric Code Sets and Others

[0240] It is desirable in some applications for the N-bit identificationword to actually signify names, companies, strange words, messages, andthe like. Most of this disclosure focuses on using the N-bitidentification word merely for high statistical security, indexedtracking codes, and other index based message carrying. The informationcarrying capacity of “invisible signatures” inside imagery and audio issomewhat limited, however, and thus it would be wise to use our N bitsefficiently if we actually want to “spell out” alphanumeric items in theN-bit identification word.

[0241] One way to do this is to define, or to use an already existing,reduced bit (e.g. less than 8-bit ASCII) standardized codes for passingalphanumeric messages. This can help to satisfy this need on the part ofsome applications. For example, a simple alphanumeric code could bebuilt on a 5-bit index table, where for example the letters V, X, Q, andZ are not included, but the digits 0 through 9 are included. In thisway, a 100 bit identification word could carry with it 20 alphanumericsymbols. Another alternative is to use variable bit length codes such asthe ones used in text compression routines (e.g. Huffman) whereby morefrequently used symbols have shorter bit length codes and lessfrequently used symbols have longer bit lengths.

[0242] More on Detecting and Recognizing the N-bit Identification Wordin Suspect Signals

[0243] Classically speaking, the detection of the N-bit identificationword fits nicely into the old art of detecting known signals in noise.Noise in this last statement can be interpreted very broadly, even tothe point where an image or audio track itself can be considered noise,relative to the need to detect the underlying signature signals. One ofmany references to this older art is the book Kassam, Saleem A., “SignalDetection in Non-Guassian Noise,” Springer-Verlag, 1988 (available atthe Library of Congress by catalog number TK5102.5.K357 1988). To thebest of this inventor's current understanding, none of the material inthis book is directly applicable to the issue of discovering thepolarity of embedded signals of this invention, but the broaderprinciples are indeed applicable.

[0244] In particular, section 1.2 “Basic Concepts of Hypothesis Testing”of Kassam's book lays out the basic concept of a binary hypothesis,assigning the value “1” to one hypothesis and the value “0” to the otherhypothesis. The last paragraph of that section is also on pointregarding the initial preferred embodiment of this invention, i.e., thatthe “0” hypothesis corresponds to “noise only” case, whereas the “1”corresponds to the presence of a signal in the observations. The currentpreferred embodiment of using true polarity is not like this however,where now the “0” corresponds to the presence of an inverted signalrather than to “noise-only.” Also in the current preferred embodiment,the case of “noise-only” is effectively ignored, and that anidentification process will either come up with our N-bit identificationword or it will come up with “garbage.”

[0245] The continued and inevitable engineering improvement in thedetection of embedded code signals will undoubtedly borrow heavily fromthis generic field of known signal detection. A common and well-knowntechnique in this field is the so-called “matched filter,” which isincidentally discussed early in section 2 of the Kassam book. Many basictexts on signal processing include discussions on this method of signaldetection. This is also known in some fields as correlation detection.Furthermore, when the phase or location of a known signal is known apriori, such as is often the case in applications of this invention,then the matched filter can often be reduced to a simple vector dotproduct between a suspect image and the embedded signal associated withan m'th bit plane in our N-bit identification word. This then representsyet another simple “detection algorithm” for taking a suspect image andproducing a sequence of 1s and 0s with the intention of determining ifthat series corresponds to a pre-embedded N-bit identification word. Inwords, and with reference to FIG. 3, we run through the process steps upthrough and including the subtracting of the original image from thesuspect, but the next step is merely to step through all N randomindependent signals and perform a simple vector dot product betweenthese signals and the difference signal, and if that dot product isnegative, assign a ‘0’ and if that dot product is positive, assign a‘1.’ Careful analysis of this “one of many” algorithms will show itssimilarity to the traditional matched filter.

[0246] There are also some immediate improvements to the “matchedfilter” and “correlation-type” that can provide enhanced ability toproperly detect very low level embedded code signals. Some of theseimprovements are derived from principles set forth in the Kassam book,others are generated by the inventor and the inventor has no knowledgeof their being developed in other papers or works, but neither has theinventor done fully extensive searching for advanced signal detectiontechniques. One such technique is perhaps best exemplified by FIG. 3.5in Kassam on page 79, wherein there are certain plots of the variouslocally optimum weighting coefficients which can apply to a generaldot-product algorithmic approach to detection. In other words, ratherthan performing a simple dot product, each elemental multiplicationoperation in an overall dot product can be weighted based upon known apriori statistical information about the difference signal itself, i.e.,the signal within which the low level known signals are being sought.The interested reader who is not already familiar with these topics isencouraged to read chapter 3 of Kassam to gain a fuller understanding.

[0247] One principle which did not seem to be explicitly present in theKassam book and which was developed rudimentarily by the inventorinvolves the exploitation of the magnitudes of the statisticalproperties of the known signal being sought relative to the magnitude ofthe statistical properties of the suspect signal as a whole. Inparticular, the problematic case seems to be where the embedded signalswe are looking for are of much lower level than the noise and corruptionpresent on a difference signal. FIG. 14 attempts to set the stage forthe reasoning behind this approach. The top FIG. 720 contains a genericlook at the differences in the histograms between a typical“problematic” difference signal, i.e., a difference signal which has amuch higher overall energy than the embedded signals that may or may notbe within it. The term “mean-removed” simply means that the means ofboth the difference signal and the embedded code signal have beenremoved, a common operation prior to performing a normalized dotproduct. The lower FIG. 722 then has a generally similar histogram plotof the derivatives of the two signals, or in the case of an image, thescalar gradients. From pure inspection it can be seen that a simplethresholding operation in the derivative transform domain, with asubsequent conversion back into the signal domain, will go a long waytoward removing certain innate biases on the dot product “recognitionalgorithm” of a few paragraphs back. Thresholding here refers to theidea that if the absolute value of a difference signal derivative valueexceeds some threshold, then it is replaced simply by that thresholdvalue. The threshold value can be so chosen to contain most of thehistogram of the embedded signal.

[0248] Another operation which can be of minor assistance in“alleviating” some of the bias effects in the dot product algorithm isthe removal of the low order frequencies in the difference signal, i.e.,running the difference signal through a high pass filter, where thecutoff frequency for the high pass filter is relatively near the origin(or DC) frequency.

[0249] Special Considerations for Recognizing Embedded Codes on SignalsWhich Have Been Compressed and Decompressed: or Alternatively, forRecognizing Embedded Codes Within Any Signal Which Has Undergone SomeKnown Process Which Creates Non-Uniform Error Sources

[0250] Long title for a basic concept. Some signal processingoperations, such as compressing and decompressing an image, as with theJPEG/MPEG formats of image/video compression, create errors in somegiven transform domain which have certain correlations and structure.Using JPEG as an example, if a given image is compressed thendecompressed at some high compression ratio, and that resulting image isthen fourier transformed and compared to the fourier transform of theoriginal uncompressed image, a definite pattern is clearly visible. Thispatterning is indicative of correlated error, i.e. error which can be tosome extent quantified and predicted. The prediction of the grosserproperties of this correlated error can then be used to advantage in theheretofore-discussed methods of recognizing the embedded code signalswithin some suspect image which may have undergone either JPEGcompression or any other operation which leaves these telltalecorrelated error signatures. The basic idea is that in areas where thereare known higher levels of error, the value of the recognition methodsis diminished relative to the areas with known lower levels ofcorrelated errors. It is often possible to quantify the expected levelsof error and use this quantification to appropriately weight theretransformed signal values. Using JPEG compression again as an example,a suspect signal can be fourier transformed, and the fourier spacerepresentation may clearly show the telltale box grid pattern. Thefourier space signal can then be “spatially filtered” near the gridpoints, and this filtered representation can then be transformed backinto its regular time or space domain to then be run through therecognition methods presented in this disclosure. Likewise, any signalprocessing method which creates non-uniform error sources can betransformed into the domain in which these error sources arenon-uniform, the values at the high points of the error sources can beattenuated, and the thusly “filtered” signal can be transformed backinto the time/space domain for standard recognition. Often this wholeprocess will include the lengthy and arduous step of “characterizing”the typical correlated error behavior in order to “design” theappropriate filtering profiles.

[0251] “Signature Codes” and “Invisible Signatures”

[0252] Briefly and for the sake of clarity, the phrases and terms“signatures,” “invisible signatures,” and “signature codes” have beenand will continue to be used to refer to the general techniques of thisinvention and often refer specifically to the composite embedded codesignal as defined early on in this disclosure.

[0253] More Details on Embedding Signature Codes into Motion Pictures

[0254] Just as there is a distinction made between the JPEG standardsfor compressing still images and the MPEG standards for compressedmotion images, so too should there be distinctions made between placinginvisible signatures into still images and placing signatures intomotion images. As with the JPEG/MPEG distinction, it is not a matter ofdifferent foundations, it is the fact that with motion images a newdimension of engineering optimization opens up by the inclusion of timeas a parameter. Any textbook dealing with MPEG will surely contain asection on how MPEG is (generally) not merely applying JPEG on a frameby frame basis. It will be the same with the application of theprinciples of this invention: generally speaking, the placement ofinvisible signatures into motion image sequences will not be simplyindependently placing invisible signatures into one frame after thenext. A variety of time-based considerations come into play, somedealing with the psychophysics of motion image perception, others drivenby simple cost engineering considerations.

[0255] One preferred embodiment is the following. This example actuallyuses the MPEG compression standard as a piece of a solution. Othermotion image compression schemes could equally well be used, be theyalready invented or yet to be invented. This example also utilizes thescrambled logo image approach to generating the master snowy image asdepicted in FIG. 13 and discussed in the disclosure.

[0256] A “compressed master snowy image” is independently rendered asdepicted in FIG. 15. “Rendered” refers to the generally well knowntechnique in video, movie and animation production whereby an image orsequence of images is created by constructive techniques such ascomputer instructions or the drawing of animation cells by hand. Thus,“to render” a signature movie in this example is essentially to leteither a computer create it as a digital file or to design some customdigital electronic circuitry to create it.

[0257] The overall goal of the procedure outlined in FIG. 15 is to applythe invisible signatures to the original movie 762 in such a way thatthe signatures do not degrade the commercial value of the movie,memorialized by the side-by-side viewing, 768, AND in such a way thatthe signature optimally survives through the MPEG compression anddecompression process. As noted earlier, the use of the MPEG process inparticular is an example of the generic process of compression. Also itshould be noted that the example presented here has definite room forengineering variations. In particular, those practiced in the art ofmotion picture compression will appreciate the fact if we start out withtwo video streams A and B, and we compress A and B separately andcombine their results, then the resultant video stream C will notgenerally be the same as if we pre-added the video streams A and B andcompressed this resultant. Thus we have in general, e.g.:

MPEG(A)+MPEG(B)=.backslash.=MPEG(A+B)

[0258] where =.backslash.= is not equal to. This is somewhat an abstractnotion to introduce at this point in the disclosure and will become moreclear as FIG. 15 is discussed. The general idea, however, is that therewill be a variety of algebras that can be used to optimize thepass-through of “invisible” signatures through compression procedures.Clearly, the same principles as depicted in FIG. 15 also work on stillimages and the JPEG or any other still image compression standard.

[0259] Turning now to the details of FIG. 15, we begin with the simplestepping through of all Z frames of a movie or video. For a two hourmovie played at 30 frames per second, Z turns out to be (30*2*60*60) or216,000. The inner loop of 700, 702 and 704 merely mimics FIG. 13'ssteps. The logo frame optionally can change during the stepping throughframes. The two arrows emanating from the box 704 represent both thecontinuation of the loop 750 and the depositing of output frames intothe rendered master Snowy Image 752.

[0260] To take a brief but potentially appropriate digression at thispoint, the use of the concept of a Markov process brings certain clarityto the discussion of optimizing the engineering implementation of themethods of FIG. 15. Briefly, a Markov process is one in which a sequenceof events takes place and in general there is no memory between one stepin the sequence and the next. In the context of FIG. 15 and a sequenceof images, a Markovian sequence of images would be one in which there isno apparent or appreciable correlation between a given frame and thenext. Imagine taking the set of all movies ever produced, stepping oneframe at a time and selecting a random frame from a random movie to beinserted into an output movie, and then stepping through, say, oneminute or 1800 of these frames. The resulting “movie” would be a fineexample of a Markovian movie. One point of this discussion is thatdepending on how the logo frames are rendered and depending on how theencryption/scrambling step 702 is performed, the Master Snowy Movie 752will exhibit some generally quantifiable degree of Markoviancharacteristics. The point of this point is that the compressionprocedure itself will be affected by this degree of Markovian nature andthus needs to be accounted for in designing the process of FIG. 15.Likewise, and only in general, even if a fully Markovian movie iscreated in the High Brightness Master Snowy Movie, 752, then theprocessing of compressing and decompressing that movie 752, representedas the MPEG box 754, will break down some of the Markovian nature of 752and create at least a marginally non-Markovian compressed master SnowyMovie 756. This point will be utilized when the disclosure brieflydiscusses the idea of using multiple frames of a video stream in orderto find a single N-bit identification word, that is, the same N-bitidentification word may be embedded into several frames of a movie, andit is quite reasonable to use the information derived from thosemultiple frames to find that single N-bit identification word. Thenon-Markovian nature of 756 thus adds certain tools to reading andrecognizing the invisible signatures. Enough of this tangent.

[0261] With the intent of preconditioning the ultimately utilized MasterSnowy Movie 756, we now send the rendered High Brightness Master SnowyMovie 752 through both the MPEG compression AND decompression procedure754. With the caveat previously discussed where it is acknowledged thatthe MPEG compression process is generally not distributive, the idea ofthe step 754 is to crudely segregate the initially rendered Snowy Movie752 into two components, the component which survives the compressionprocess 754 which is 756, and the component which does not survive, alsocrudely estimated using the difference operation 758 to produce the“Cheap Master Snowy Movie” 760. The reason use is made of thedeliberately loose term “Cheap” is that we can later add this signaturesignal as well to a distributable movie, knowing that it probably won'tsurvive common compression processes but that nevertheless it canprovide “cheap” extra signature signal energy for applications orsituations which will never experience compression. >Thus it is at leastnoted in FIG. 15!. Back to FIG. 15 proper, we now have a rough cut atsignatures which we know have a higher likelihood of surviving intactthrough the compression process, and we use this “Compressed MasterSnowy Movie” 756 to then go through this invention's procedure of beingscaled down 764, added to the original movie 766, producing a candidatedistributable movie 770, then compared to the original movie (768) toensure that it meets whatever commercially viable criteria which havebeen set up (i.e. the acceptable perceived noise level). The arrow fromthe side-by-side step 768 back to the scale down step 764 correspondsquite directly to the “experiment visually. . . . ” step of FIG. 2, andthe gain control 226 of FIG. 6. Those practiced in the art of image andaudio information theory can recognize that the whole of FIG. 15 can besummarized as attempting to pre-condition the invisible signaturesignals in such a way that they are better able to withstand even quiteappreciable compression. To reiterate a previously mentioned item aswell, this idea equally applies to ANY such pre-identifiable process towhich an image, and image sequence, or audio track might be subjected.This clearly includes the JPEG process on still images.

[0262] Additional Elements of the Realtime Encoder Circuitry

[0263] It should be noted that the method steps represented in FIG. 15,generally following from box 750 up through the creation of thecompressed master snowy movie 756, could with certain modification beimplemented in hardware. In particular, the overall analog noise source206 in FIG. 6 could be replaced by such a hardware circuit. Likewise thesteps and associated procedures depicted in FIG. 13 could be implementedin hardware and replace the analog noise source 206.

[0264] Recognition based on more than one frame: non-Markoviansignatures

[0265] As noted in the digression on Markov and non-Markov sequences ofimages, it is pointed out once again that in such circumstances wherethe embedded invisible signature signals are non-Markovian in nature,i.e., that there is some correlation between the master snowy image ofone frame to that of the next, AND furthermore that a single N-bitidentification word is used across a range of frames and that thesequence of N-bit identification words associated with the sequence offrames is not Markovian in nature, then it is possible to utilize thedata from several frames of a movie or video in order to recognize asingle N-bit identification word. All of this is a fancy way of sayingthat the process of recognizing the invisible signatures should use asmuch information as is available, in this case translating to multipleframes of a motion image sequence.

[0266] Header Verification

[0267] The concept of the “header” on a digital image or audio file is awell established practice in the art. The top of FIG. 16 has asimplified look at the concept of the header, wherein a data file beginswith generally a comprehensive set of information about the file as awhole, often including information about who the author or copyrightholder of the data is, if there is a copyright holder at all. Thisheader 800 is then typically followed by the data itself 802, such as anaudio stream, a digital image, a video stream, or compressed versions ofany of these items. This is all exceedingly known and common in theindustry.

[0268] One way in which the principles of this invention can be employedin the service of information integrity is generically depicted in thelower diagram of FIG. 16. In general, the N-bit identification word canbe used to essentially “wallpaper” a given simple message throughout animage (as depicted) or audio data stream, thereby reinforcing somemessage already contained in a traditional header. This is referred toas “header verification” in the title of this section. The thinking hereis that less sophisticated would-be pirates and abusers can alter theinformation content of header information, and the more securetechniques of this inventions can thus be used as checks on the veracityof header information. Provided that the code message, such as “joe'simage” in the header, matches the repeated message throughout an image,then a user obtaining the image can have some higher degree ofconfidence that no alteration of the header has taken place.

[0269] Likewise, the header can actually carry the N-bit identificationword so that the fact that a given data set has been coded via themethods of this invention can be highlighted and the verification codebuilt right into the header. Naturally, this data file format has notbeen created yet since the principles of this invention are currentlynot being employed.

[0270] The “Bodier”: The Ability to Largely Replace a Header

[0271] Although all of the possible applications of the following aspectof the invention are not fully developed, it is nevertheless presentedas a design alternative that may be important some day. The title ofthis section contains the silly phrase used to describe thispossibility: the “bodier.”

[0272] Whereas the previous section outlined how the N-bitidentification word could “verify” information contained within theheader of a digital file, there is also the prospect that the methods ofthis invention could completely replace the very concept of the headerand place the information which is traditionally stored in the headerdirectly into the digital signal and empirical data itself.

[0273] This could be as simple as standardizing on, purely for example,a 96-bit (12 bytes) leader string on an otherwise entirely empiricaldata stream. This leader string would plain and simple contain thenumeric length, in elemental data units, of the entire data file notincluding the leader string, and the number of bits of depth of a singledata element (e.g. its number of grey levels or the number of discretesignal levels of an audio signal). From there, universal codes asdescribed in this specification would be used to read the N-bitidentification word written directly within the empirical data. Thelength of the empirical data would need to be long enough to contain thefull N bits. The N-bit word would effectively transmit what wouldotherwise be contained in a traditional header.

[0274]FIG. 17 depicts such a data format and calls it the “universalempirical data format.” The leader string 820 is comprised of the 64 bitstring length 822 and the 32 bit data word size 824. The data stream 826then immediately follows, and the information traditionally contained inthe header but now contained directly in the data stream is representedas the attached dotted line 828. Another term used for this attachedinformation is a “shadow channel” as also depicted in FIG. 17.

[0275] Yet another element that may need to be included in the leaderstring is some sort of complex check sum bits which can verify that thewhole of the data file is intact and unaltered. This is not included inFIG. 17.

[0276] More on Distributed Universal Code Systems: Dynamic Codes

[0277] One intriguing variation on the theme of universal codes is thepossibility of the N-bit identification word actually containinginstructions which vary the operations of the universal code systemitself. One of many examples is immediately in order: a datatransmission is begun wherein a given block of audio data is fullytransmitted, an N-bit identification word is read knowing that the firstblock of data used universal codes #145 out of a set of 500, say, andthat part of the N-bit identification word thus found is theinstructions that the next block of data should be “analyzed” using theuniversal code set #411 rather than # 145. In general, this inventioncan thus be used as a method for changing on the fly the actual decodinginstructions themselves. Also in general, this ability to utilize“dynamic codes” should greatly increase the sophistication level of thedata verification procedures and increase the economic viability ofsystems which are prone to less sophisticated thwarting by hackers andwould-be pirates. The inventor does not believe that the concept ofdynamically changing decoding/decrypting instructions is novel per se,but the carrying of those instructions on the “shadow channel” ofempirical data does appear to be novel to the best of the inventor'sunderstanding. >Shadow channel was previously defined as yet anothervernacular phrase encapsulating the more steganographic proper elementsof this invention!.

[0278] A variant on the theme of dynamic codes is the use of universalcodes on systems which have a priori assigned knowledge of which codesto use when. One way to summarize this possibility is the idea of “thedaily password.” The password in this example represents knowledge ofwhich set of universal codes is currently operative, and these changedepending on some set of application-specific circumstances. Presumablymany applications would be continually updating the universal codes toones which had never before been used, which is often the case with thetraditional concept of the daily password. Part of a currentlytransmitted N-bit identification word could be the passing on of thenext day's password, for example. Though time might be the most commontrigger events for the changing of passwords, there could be event basedtriggers as well.

[0279] Symmetric Patterns and Noise Patterns: Toward a Robust UniversalCoding System

[0280] The placement of identification patterns into images is certainlynot new. Logos stamped into comers of images, subtle patterns such astrue signatures or the wallpapering of the copyright circle-C symbol,and the watermark proper are all examples of placing patterns intoimages in order to signify ownership or to try to prevent illicit usesof the creative material.

[0281] What does appear to be novel is the approach of placingindependent “carrier” patterns, which themselves are capable of beingmodulated with certain information, directly into images and audio forthe purposes of transmission and discernment of said information, whileeffectively being imperceptible and/or unintelligible to a perceivinghuman. Steganographic solutions currently known to the inventor allplace this information “directly” into empirical data (possibly firstencrypted, then directly), whereas the methods of this disclosure positthe creation of these (most-often) coextensive carrier signals, themodulation of those carrier signals with the information proper, THENthe direct application to the empirical data.

[0282] In extending these concepts one step further into the applicationarena of universal code systems, where a sending site transmitsempirical data with a certain universal coding scheme employed and areceiving site analyzes said empirical data using the universal codingscheme, it would be advantageous to take a closer look at theengineering considerations of such a system designed for thetransmission of images or motion images, as opposed to audio. Said moreclearly, the same type of analysis of a specific implementation such asis contained in FIG. 9 and its accompanying discussion on the universalcodes in audio applications should as well be done on imagery (or twodimensional signals). This section is such an analysis and outline of aspecific implementation of universal codes and it attempts to anticipatevarious hurdles that such a method should clear.

[0283] The unifying theme of one implementation of a universal codingsystem for imagery and motion imagery is “symmetry.” The idea drivingthis couldn't be more simple: a prophylactic against the use of imagerotation as a means for less sophisticated pirates to bypass any givenuniversal coding system. The guiding principle is that the universalcoding system should easily be read no matter what rotationalorientation the subject imagery is in. These issues are quite common inthe fields of optical character recognition and object recognition, andthese fields should be consulted for further tools and tricks infurthering the engineering implementation of this invention. As usual,an immediate example is in order.

[0284] Digital Video And Internet Company XYZ has developed a deliverysystem of its product which relies on a non-symmetric universal codingwhich double checks incoming video to see if the individual frames ofvideo itself, the visual data, contain XYZ's own relatively highsecurity internal signature codes using the methods of this invention.This works well and fine for many delivery situations, including theirInternet tollgate which does not pass any material unless both theheader information is verified AND the in-frame universal codes arefound. However, another piece of their commercial network performsmundane routine monitoring on Internet channels to look for unauthorizedtransmission of their proprietary creative property. They control theencryption procedures used, thus it is no problem for them to unencryptcreative property, including headers, and perform straightforwardchecks. A pirate group that wants to traffic material on XYZ's networkhas determined how to modify the security features in XYZ's headerinformation system, and they have furthermore discovered that by simplyrotating imagery by 10 or 20 degrees, and transmitting it over XYZ'snetwork, the network doesn't recognize the codes and therefore does notflag illicit uses of their material, and the receiver of the pirate'srotated material simply unrotates it.

[0285] Summarizing this last example via logical categories, thenon-symmetric universal codes are quite acceptable for the “enablementof authorized action based on the finding of the codes,” whereas it canbe somewhat easily by-passed in the case of “random monitoring(policing) for the presence of codes.”)Bear in mind that thenon-symmetric universal codes may very well catch 90% of illicit uses,i.e. 90% of the illicit users wouldn't bother even going to the simpleby-pass of rotation.! To address this latter category, the use ofquasi-rotationally symmetric universal codes is called for. “Quasi”derives from the age old squaring the circle issue, in this instancetranslating into not quite being able to represent a full incrementallyrotational symmetric 2-D object on a square grid of pixels. Furthermore,basic considerations must be made for scale/magnification changes of theuniversal codes. It is understood that the monitoring process must beperformed when the monitored visual material is in the “perceptual”domain, i.e. when it has been unencrypted or unscrambled and in the formwith which it is (or would be) presented to a human viewer. Would-bepirates could attempt to use other simple visual scrambling andunscrambling techniques, and tools could be developed to monitor forthese telltale scrambled signals. Said another way, would-be pirateswould then look to transform visual material out of the perceptualdomain, pass by a monitoring point, and then transform the material backinto the perceptual domain; tools other than the monitoring foruniversal codes would need to be used in such scenarios. The monitoringdiscussed here therefore applies to applications where monitoring can beperformed in the perceptual domain, such as when it is actually sent toviewing equipment.

[0286] The “ring” is the only full rotationally symmetric twodimensional object. The “disk” can be seen as a simple finite series ofconcentric and perfectly abutted rings having width along their radialaxis. Thus, the “ring” needs to be the starting point from which a morerobust universal code standard for images is found. The ring also willfit nicely into the issue of scale/magnification changes, where theradius of a ring is a single parameter to keep track of and account for.Another property of the ring is that even the case where differentialscale changes are made to different spatial axes in an image, and thering turns into an oval, many of the smooth and quasi-symmetricproperties that any automated monitoring system will be looking for aregenerally maintained. Likewise, appreciable geometric distortion of anyimage will clearly distort rings but they can still maintain grosssymmetric properties. Hopefully, more pedestrian methods such as simply“viewing” imagery will be able to detect attempted illicit piracy inthese regards, especially when such lengths are taken to by-pass theuniversal coding system.

[0287] Rings to Knots

[0288] Having discovered the ring as the only ideal symmetric patternupon whose foundation a full rotationally robust universal coding systemcan be built, we must turn this basic pattern into something functional,something which can carry information, can be read by computers andother instrumentation, can survive simple transformations andcorruptions, and can give rise to reasonably high levels of security(probably not unbreakable, as the section on universal codes explained)in order to keep the economics of subversion as a simple incrementalcost item.

[0289] One current preferred embodiment of the “ring-based” universalcodes is what the inventor refers to as “knot patterns” or simply“knots,” in deference to woven Celtic knot patterns which were laterrefined and exalted in the works of Leonardo Da Vinci (e.g. Mona Lisa,or his knot engravings). Some rumors have it that these drawings ofknots were indeed steganographic in nature, i.e. conveying messages andsignatures; all the more appropriate. FIGS. 18 and 19 explore some ofthe fundamental properties of these knots.

[0290] Two simple examples of knot patterns are depicted by thesupra-radial knots, 850 and the radial knots 852. The names of thesetypes are based on the central symmetry point of the splayed rings andwhether the constituent rings intersect this point, are fully outsideit, or in the case of sub-radial knots the central point would be insidea constituent circle. The examples of 850 and 852 clearly show asymmetrical arrangement of 8 rings or circles. “Rings” is the moreappropriate term, as discussed above, in that this term explicitlyacknowledges the width of the rings along the radial axis of the ring.It is each of the individual rings in the knot patterns 850 and 852which will be the carrier signal for a single associated bit plane inour N-bit identification word. Thus, the knot patterns 850 and 852 eachare an 8-bit carrier of information. Specifically, assuming now that theknot patterns 850 and 852 are luminous rings on a black background, thenthe “addition” of a luminous ring to an independent source image couldrepresent a “1” and the “subtraction” of a luminous ring from anindependent source image could represent a “0.” The application of thissimple encoding scheme could then be replicated over and over as in FIG.19 and its mosaic of knot patterns, with the ultimate step of adding ascaled down version of this encoded (modulated) knot mosaic directly andcoextensively to the original image, with the resultant being thedistributable image which has been encoded via this universal symmetriccoding method. It remains to communicate to a decoding system which ringis the least significant bit in our N-bit identification word and whichis the most significant. One such method is to make a slightly ascendingscale of radii values (of the individual rings) from the LSB to the MSB.Another is to merely make the MSB, say, 10% larger radius than all theothers and to pre-assign counterclockwise as the order with which theremaining bits fall out. Yet another is to put some simple hash markinside one and only one circle. In other words, there are a variety ofways with which the bit order of the rings can be encoded in these knotpatterns.

[0291] The preferred embodiment for the decoding of, first of allchecking for the mere existence of these knot patterns, and second, forthe reading of the N-bit identification word, is as follows. A suspectimage is first fourier transformed via the extremely common 2D FFTcomputer procedure. Assuming that we don't know the exact scale of theknot patterns, i.e., we don't know the radius of an elemental ring ofthe knot pattern in the units of pixels, and that we don't know theexact rotational state of a knot pattern, we merely inspect (via basicautomated pattern recognition methods) the resulting magnitude of theFourier transform of the original image for telltale ripple patterns(concentric low amplitude sinusoidal rings on top of the spatialfrequency profile of a source image). The periodicity of these rings,along with the spacing of the rings, will inform us that the universalknot patterns are or are not likely present, and their scale in pixels.Classical small signal detection methods can be applied to this problemjust as they can to the other detection methodologies of thisdisclosure. Common spatial filtering can then be applied to the fouriertransformed suspect image, where the spatial filter to be used wouldpass all spatial frequencies which are on the crests of the concentriccircles and block all other spatial frequencies. The resulting filteredimage would be fourier transformed out of the spatial frequency domainback into the image space domain, and almost by visual inspection theinversion or non-inversion of the luminous rings could be detected,along with identification of the MSB or LSB ring, and the (in this case8) N-bit identification code word could be found. Clearly, a patternrecognition procedure could perform this decoding step as well.

[0292] The preceding discussion and the method it describes has certainpractical disadvantages and shortcomings which will now be discussed andimproved upon. The basic method was presented in a simpleminded fashionin order to communicate the basic principles involved.

[0293] Let's enumerate a few of the practical difficulties of the abovedescribed universal coding system using the knot patterns. For one (1),the ring patterns are somewhat inefficient in their “covering” of thefull image space and in using all of the information carrying capacityof an image extent. Second (2), the ring patterns themselves will almostneed to be more visible to the eye if they are applied, say, in astraightforward additive way to an 8-bit black and white image. Next(3), the “8” rings of FIG. 18, 850 and 852, is a rather low number, andmoreover, there is a 22 and one half degree rotation which could beapplied to the figures which the recognition methods would need tocontend with (360 divided by 8 divided by 2). Next (4), strictoverlapping of rings would produce highly condensed areas where theadded and subtracted brightness could become quite appreciable. Next(5), the 2D FFT routine used in the decoding is notoriouslycomputationally cumbersome as well as some of the pattern recognitionmethods alluded to. Finally (6), though this heretofore described formof universal coding does not pretend to have ultra-high security in theclassical sense of top security communications systems, it wouldnevertheless be advantageous to add certain security features whichwould be inexpensive to implement in hardware and software systems whichat the same time would increase the cost of would-be pirates attemptingto thwart the system, and increase the necessary sophistication level ofthose pirates, to the point that a would-be pirate would have to go sofar out of their way to thwart the system that willfulness would beeasily proven and hopefully subject to stiff criminal liability andpenalty (such as the creation and distribution of tools which stripcreative property of these knot pattern codes).

[0294] All of these items can be addressed and should continue to berefined upon in any engineering implementation of the principles of theinvention. This disclosure addresses these items with the followingcurrent preferred embodiments.

[0295] Beginning with item number 3, that there are only 8 ringsrepresented in FIG. 18 is simply remedied by increasing the number ofrings. The number of rings that any given application will utilize isclearly a function of the application. The trade-offs include but arenot limited to: on the side which argues to limit the number of ringsutilized, there will ultimately be more signal energy per ring (pervisibility) if there are less rings; the rings will be less crowded sothat there discernment via automated recognition methods will befacilitated; and in general since they are less crowded, the full knotpattern can be contained using a smaller overall pixel extent, e.g. a 30pixel diameter region of image rather than a 100 pixel diameter region.The arguments to increase the number of rings include: the desire totransmit more information, such as ascii information, serial numbers,access codes, allowed use codes and index numbers, history information,etc.; another key advantage of having more rings is that the rotation ofthe knot pattern back into itself is reduced, thereby allowing therecognition methods to deal with a smaller range of rotation angles(e.g., 64 rings will have a maximum rotational displacement of justunder 3 degrees, i.e. maximally dissimilar to its original pattern,where a rotation of about 5 and one half degrees brings the knot patternback into its initial alignment; the need to distinguish the MSB/LSB andthe bit plane order is better seen in this example as well). It isanticipated that most practical applications will choose between 16 and128 rings, corresponding to N=16 to N=128 for the choice of the numberof bits in the N-bit identification code word. The range of this choicewould somewhat correlate to the overall radius, in pixels, allotted toan elemental knot pattern such as 850 or 852.

[0296] Addressing the practical difficulty item number 4, that of thecondensation of rings patterns at some points in the image and lack ofring patterns in others (which is very similar, but still distinct from,item 1, the inefficient covering), the following improvement can beapplied. FIG. 18 shows an example of a key feature of a “knot” (asopposed to a pattern of rings) in that where patterns would supposedlyintersect, a virtual third dimension is posited whereby one strand ofthe knot takes precedence over another strand in some predefined way;see item 854. In the terms of imagery, the brightness or dimness of agiven intersection point in the knot patterns would be “assigned” to oneand only one strand, even in areas where more than two strands overlap.The idea here is then extended, 864, to how rules about this assignmentshould be carried out in some rotationally symmetric manner. Forexample, a rule would be that, travelling clockwise, an incoming strandto a loop would be “behind” an outgoing strand. Clearly there are amultitude of variations which could be applied to these rules, manywhich would critically depend on the geometry of the knot patternschosen. Other issues involved will probably be that the finite width,and moreover the brightness profile of the width along the normal axisto the direction of a strand, will all play a role in the rules ofbrightness assignment to any given pixel underlying the knot patterns.

[0297] A major improvement to the nominal knot pattern system previouslydescribed directly addresses practical difficulties (1), the inefficientcovering, (2) the unwanted visibility of the rings, and (6) the need forhigher levels of security. This improvement also indirectly address item(4) the overlapping issue, which has been discussed in the lastparagraph. This major improvement is the following: just prior to thestep where the mosaic of the encoded knot patterns is added to anoriginal image to produce a distributable image, the mosaic of encodedknot patterns, 866, is spatially filtered (using common 2D FFTtechniques) by a standardized and (generally smoothly) random phase-onlyspatial filter. It is very important to note that this phase-only filteris itself fully rotationally symmetric within the spatial frequencydomain, i.e. its filtering effects are fully rotationally symmetric. Theeffect of this phase-only filter on an individual luminous ring is totransform it into a smoothly varying pattern of concentric rings, nottotally dissimilar to the pattern on water several instances after apebble is dropped in, only that the wave patterns are somewhat random inthe case of this phase-only filter rather than the uniform periodicityof a pebble wave pattern. FIG. 20 attempts to give a rough (i.e.non-greyscale) depiction of these phase-only filtered ring patterns. Thetop figure of FIG. 20 is a cross section of a typical brightnesscontour/profile 874 of one of these phase-only filtered ring patterns.Referenced in the figure is the nominal location of the pre-filteredouter ring center, 870. The center of an individual ring, 872, isreferenced as the point around which the brightness profile is rotatedin order to fully describe the two dimensional brightness distributionof one of these filtered patterns. Yet another rough attempt tocommunicate the characteristics of the filtered ring is depicted as 876,a crude greyscale image of the filtered ring. This phase-only filteredring, 876 will be referred to as a random ripple pattern.

[0298] Not depicted in FIG. 20 is the composite effects of phase-onlyfiltering on the knot patterns of FIG. 18, or on the mosaic of knotpatterns 866 in FIG. 19. Each of the individual rings in the knotpatterns 850 or 852 will give rise to a 2D brightness pattern of thetype 876, and together they form a rather complicated brightnesspattern. Realizing that the encoding of the rings is done by making itluminous (1) or “anti-luminous” (0), the resulting phase-only filteredknot patterns begin to take on subtle characteristics which no longermake direct sense to the human eye, but which are still readilydiscernable to a computer especially after the phase-only filtering isinverse filtered reproducing the original rings patterns.

[0299] Returning now to FIG. 19, we can imagine that an 8-bitidentification word has been encoded on the knot patterns and the knotpatterns phase-only filtered. The resulting brightness distributionwould be a rich tapestry of overlapping wave patterns which would have acertain beauty, but would not be readily intelligible to theeye/brain. >An exception to this might draw from the lore of the SouthPacific Island communities, where it is said that sea travellers havelearned the subtle art of reading small and multiply complex ocean wavepatterns, generated by diffracted and reflected ocean waves off ofintervening islands, as a primary navigational tool.! For want of abetter term, the resulting mosaic of filtered knot patterns (derivedfrom 866) can be called the encoded knot tapestry or just the knottapestry. Some basic properties of this knot tapestry are that itretains the basic rotational symmetry of its generator mosaic, it isgenerally unintelligible to the eye/brain, thus raising it a notch onthe sophistication level of reverse engineering, it is more efficient atusing the available information content of a grid of pixels (more onthis in the next section), and if the basic knot concepts 854 and 864are utilized, it will not give rise to local “hot spots” where thesignal level becomes unduly condensed and hence objectionably visible toa viewer.

[0300] The basic decoding process previously described would now needthe additional step of inverse filtering the phase-only filter used inthe encoding process. This inverse filtering is quite well known in theimage processing industry. Provided that the scale of the knot patternsare known a priori, the inverse filtering is straightforward. If on theother hand the scale of the knot patterns is not known, then anadditional step of discovering this scale is in order. One such methodof discovering the scale of the knot patterns is to iteratively applythe inverse phase-only filter to variously scaled version of an imagebeing decoded, searching for which scale-version begins to exhibitnoticeable knot patterning. A common search algorithm such as thesimplex method could be used in order to accurately discover the scaleof the patterns. The field of object recognition should also beconsulted, under the general topic of unknown-scale object detection.

[0301] An additional point about the efficiency with which the knottapestry covers the image pixel grid is in order. Most applications ofthe knot tapestry method of universal image coding will posit theapplication of the fully encoded tapestry (i.e. the tapestry which hasthe N-bit identification word embedded) at a relative low brightnesslevel into the source image. In real terms, the brightness scale of theencoded tapestry will vary from, for example, −5 grey scale values to 5grey scale values in a typical 256 grey scale image, where thepreponderance of values will be within −2 and 2. This brings up thepurely practical matter that the knot tapestry will be subject toappreciable bit truncation error. Put as an example, imagine aconstructed knot tapestry nicely utilizing a full 256 grey level image,then scaling this down by a factor of 20 in brightness including the bittruncation step, then resealing this truncated version back up inbrightness by the same factor of 20, then inverse phase-only filteringthe resultant. The resulting knot pattern mosaic will be a noticeablydegraded version of the original knot pattern mosaic. The point ofbringing all of this up is the following: it will be a simply defined,but indeed challenging, engineering task to select the various freeparameters of design in the implementation of the knot tapestry method,the end goal being to pass a maximum amount of information about theN-bit identification word within some pre-defined visibility toleranceof the knot tapestry. The free parameters include but would not be fullylimited to: the radius of the elemental ring in pixels, N or the numberof rings, the distance in pixels from the center of a knot pattern tothe center of an elemental ring, the packing criteria and distances ofone knot pattern with the others, the rules for strand weaving, and theforms and types of phase-only filters to be used on the knot mosaics. Itwould be desirable to feed such parameters into a computer optimizationroutine which could assist in their selection. Even this would beginsurely as more of an art than a science due to the many non-linear freeparameters involved.

[0302] A side note on the use of phase-only filtering is that it canassist in the detection of the ring patterns. It does so in that theinverse filtering of the decoding process tends to “blur” the underlyingsource image upon which the knot tapestry is added, while at the sametime “bringing into focus” the ring patterns. Without the blurring ofthe source image, the emerging ring patterns would have a harder time“competing” with the sharp features of typical images. The decodingprocedure should also utilize the gradient thresholding method describedin another section. Briefly, this is the method where if it is knownthat a source signal is much larger in brightness than our signaturesignals, then an image being decoded can have higher gradient areasthresholded in the service of increasing the signal level of thesignature signals relative to the source signal.

[0303] As for the other practical difficulty mentioned earlier, item (5)which deals with the relative computational overhead of the 2D FFTroutine and of typical pattern recognition routines, the first remedyhere posited but not filled is to find a simpler way of quicklyrecognizing and decoding the polarity of the ring brightnesses than thatof using the 2D FFT. Barring this, it can be seen that if the pixelextent of an individual knot pattern (850 or 852) is, for example, 50pixels in diameter, than a simple 64 by 64 pixel 2D FFT on some sectionof an image may be more than sufficient to discern the N-bitidentification word as previously described. The idea would be to usethe smallest image region necessary, as opposed to being required toutilize an entire image, to discern the N-bit identification word.

[0304] Another note is that those practitioners in the science of imageprocessing will recognize that instead of beginning the discussion onthe knot tapestry with the utilization of rings, we could have insteadjumped right to the use of 2D brightness distribution patterns 876, QUAbases functions. The use of the “ring” terminology as the baselineinvention is partly didactic, as is appropriate for patent disclosuresin any event. What is more important, perhaps, is that the use of true“rings” in the decoding process, post-inverse filtering, is probably thesimplest form to input into typical pattern recognition routines.

[0305] Neural Network Decoders

[0306] Those skilled in the signal processing art will recognize thatcomputers employing neural network architectures are well suited to thepattern recognition and detection-of-small-signal-in-noise issues posedby the present invention. While a complete discourse on these topics isbeyond the scope of this specification, the interested reader isreferred to, e.g., Cherkassky, V., “From Statistics to Neural Networks:Theory & Pattern Recognition Applications,” Springer-Verlag, 1994;Masters, T., “Signal & Image Processing with Neural Networks: CSourcebook,” Wiley, 1994; Guyon, I., “Advances in Pattern RecognitionSystems Using Neural Networks,” World Scientific Publishers, 1994;Nigrin, A., “Neural Networks for Pattern Recognition,” MIT Press, 1993;Cichoki, A., “Neural Networks for Optimization & Signal Processing,”Wiley, 1993; and Chen, C., “Neural Networks for Pattern Recognition &Their Applications,” World Scientic Publishers, 1991.

[0307] 2D Universal Codes II: Simple Scan Line Implementation of the OneDimensional Case

[0308] The above section on rings, knots and tapestries certainly hasits beauty, but some of the steps involved may have enough complexitythat practical implementations may be too costly for certainapplications. A poor cousin of the concept of rings and well-designedsymmetry is to simply utilize the basic concepts presented in connectionwith FIG. 9 and the audio signal, and apply them to two dimensionalsignals such as images, but to do so in a manner where, for example,each scan line in an image has a random starting point on, for example,a 1000 pixel long universal noise signal. It would then be incumbentupon recognition software and hardware to interrogate imagery across thefull range of rotational states and scale factors to “find” theexistence of these universal codes.

[0309] The Universal Commercial Copyright (UCC) Image, Audio, and VideoFile Formats

[0310] It is as well known as it is regretted that there exist aplethora of file format standards (and not-so-standards) for digitalimages, digital audio, and digital video. These standards have generallybeen is formed within specific industries and applications, and as theusage and exchange of creative digital material proliferated, thevarious file formats slugged it out in cross-disciplinary arenas, wheretoday we find a de facto histogram of devotees and users of the variousfavorite formats. The JPEG, MPEG standards for formatting andcompression are only slight exceptions it would seem, where someconcerted cross-industry collaboration came into play.

[0311] The cry for a simple universal standard file format foraudio/visual data is as old as the hills. The cry for the protection ofsuch material is older still. With all due respect to the innatedifficulties attendant upon the creation of a universal format, and withall due respect to the pretentiousness of outlining such a plan within apatent disclosure, the inventor does believe that the methods of thisinvention can serve perhaps as well as anything for being the foundationupon which an accepted world-wide “universal commercial copyrights”format is built. Practitioners know that such animals are not built byproclamation, but through the efficient meeting of broad needs,tenacity, and luck. More germane to the purposes of this disclosure isthe fact that the application of this invention would benefit if itcould become a central piece within an industry standard file format.The use of universal codes in particular could be specified within sucha standard. The fullest expression of the commercial usage of thisinvention comes from the knowledge that the invisible signing is takingplace and the confidence that instills in copyright holders.

[0312] The following is a list of reasons that the principles of thisinvention could serve as the catalyst for such a standard: (1) Few ifany technical developments have so isolated and so pointedly addressedthe issue of broadbrush protection of empirical data and audio/visualmaterial; (2) All previous file formats have treated the informationabout the data, and the data itself, as two separate and physicallydistinct entities, whereas the methods of this invention can combine thetwo into one physical entity; (3) The mass scale application of theprinciples of this invention will require substantial standardizationwork in the first place, including integration with the years-to-comeimprovements in compression technologies, so the standardsinfrastructure will exist by default; (4) the growth of multimedia hascreated a generic class of data called “content,” which includes text,images, sound, and graphics, arguing for higher and higher levels of“content standards”; and (5) marrying copyright protection technologyand security features directly into a file format standard is longoverdue.

[0313] Elements of a universal standard would certainly include themirroring aspects of the header verification methods, where headerinformation is verified by signature codes directly within data. Also, auniversal standard would outline how hybrid uses of fully private codesand public codes would commingle. Thus, if the public codes were“stripped” by sophisticated pirates, the private codes would remainintact. A universal standard would specify how invisible signatureswould evolve as digital images and audio evolve. Thus, when a givenimage is created based on several source images, the standard wouldspecify how and when the old signatures would be removed and replaced bynew signatures, and if the header would keep track of these evolutionsand if the signatures themselves would keep some kind of record.

[0314] Pixels Vs. Bumps

[0315] Most of the disclosure focuses on pixels being the basic carriersof the N-bit identification word. The section discussing the use of asingle “master code signal” went so far as to essentially “assign” eachand every pixel to a unique bit plane in the N-bit identification word.

[0316] For many applications, with one exemplar being that of ink basedprinting at 300 dots per inch resolution, what was once a pixel in apristine digital image file becomes effectively a blob (e.g. of ditheredink on a piece of paper). Often the isolated information carryingcapacity of the original pixel becomes compromised by neighboring pixelsspilling over into the geometrically defined space of the originalpixel. Those practiced in the art will recognize this as simple spatialfiltering and various forms of blurring.

[0317] In such circumstances it may be more advantageous to assign acertain highly local group of pixels to a unique bit plane in the N-bitidentification word, rather than merely a single pixel. The end goal issimply to preconcentrate more of the signature signal energy into thelower frequencies, realizing that most practical implementations quicklystrip or mitigate higher frequencies.

[0318] A simple-minded approach would be to assign a 2 by 2 block ofpixels all to be modulated with the same ultimate signature grey value,rather than modulating a single assigned pixel. A more fancy approach isdepicted in FIG. 21, where an array of pixel groups is depicted. This isa specific example of a large class of configurations. The idea is thatnow a certain small region of pixels is associated with a given uniquebit plane in the N-bit identification word, and that this groupingactually shares pixels between bit planes (though it doesn't necessaryhave to share pixels, as in the case of a 2×2 block of pixels above).

[0319] Depicted in FIG. 21 is a 3×3 array of pixels with an examplenormalized weighting (normalized.fwdarw.the weights add up to 1). Themethods of this invention now operate on this elementary “bump,” as aunit, rather than on a single pixel. It can be seen that in this examplethere is a fourfold decrease in the number of master code values thatneed to be stored, due to the spreading out of the signature signal.Applications of this “bump approach” to placing in invisible signaturesinclude any application which will experience a priori known highamounts of blurring, where proper identification is still desired evenafter this heavy blurring.

[0320] More on the Steganographic Uses of this Invention

[0321] As mentioned in the initial sections of the disclosure,steganography as an art and as a science is a generic prior art to thisinvention. Putting the shoe on the other foot now, and as alreadydoubtless apparent to the reader who has ventured thus far, the methodsof this invention can be used as a novel method for performingsteganography. (Indeed, all of the discussion thus far may be regardedas exploring various forms and implementations of steganography.)

[0322] In the present section, we shall consider steganography as theneed to pass a message from point A to point B, where that message isessentially hidden within generally independent empirical data. Asanyone in the industry of telecommunications can attest to, the range ofpurposes for passing messages is quite broad. Presumably there would besome extra need, beyond pure hobby, to place messages into empiricaldata and empirical signals, rather than sending those messages via anynumber of conventional and straightforward channels. Past literature andproduct propaganda within steganography posits that such an extra need,among others, might be the desire to hide the fact that a message iseven being sent. Another possible need is that a conventionalcommunications channel is not available directly or is cost prohibitive,assuming, that is, that a sender of messages can “transmit” theirencoded empirical data somehow. This disclosure includes by referenceall previous discussions on the myriad uses to which steganography mightapply, while adding the following uses which the inventor has notpreviously seen described.

[0323] The first such use is very simple. It is the need to carrymessages about the empirical data within which the message is carried.The little joke is that now the media is truly the message, though itwould be next to impossible that some previous steganographer hasn'talready exploited this joke. Some of the discussion on placinginformation about the empirical data directly inside that empirical datawas already covered in the section on replacing the header and theconcept of the “bodier.” This section expands upon that sectionsomewhat.

[0324] The advantages of placing a message about empirical data directlyin that data is that now only one class of data object is present ratherthan the previous two classes. In any two class system, there is therisk of the two classes becoming disassociated, or one class corruptedwithout the other knowing about it. A concrete example here is what theinventor refers to as “device independent instructions.” There existzillions of machine data formats and data file formats. This plethora offormats has been notorious in its power to impede progress towarduniversal data exchange and having one machine do the same thing thatanother machine can do. The instructions that an originator might putinto a second class of data (say the header) may not at all becompatible with a machine which is intended to recognize theseinstructions. If format conversions have taken place, it is alsopossible that critical instructions have been stripped along the way, orgarbled. The improvements disclosed here can be used as a way to “sealin” certain instructions directly into empirical data in such a way thatall that is needed by a reading machine to recognize instructions andmessages is to perform a standardized “recognition algorithm” on theempirical data (providing of course that the machine can at the veryleast “read” the empirical data properly). All machines could implementthis algorithm any old way they choose, using any compilers or internaldata formats that they want.

[0325] Implementation of this device independent instruction methodwould generally not be concerned over the issue of piracy or illicitremoval of the sealed in messages. Presumably, the embedded messages andinstructions would be a central valuable component in the basic valueand functioning of the material.

[0326] Another example of a kind of steganographic use of the inventionis the embedding of universal use codes for the benefit of a usercommunity. The “message” being passed could be simply a registeredserial number identifying ownership to users who wish to legitimatelyuse and pay for the empirical information. The serial number could indexinto a vast registry of creative property, containing the name or namesof the owners, pricing information, billing information, and the like.The “message” could also be the clearance of free and public use forsome given material. Similar ownership identification and use indexingcan be achieved in two class data structure methods such as a header,but the use of the single class system of this invention may offercertain advantages over the two class system in that the single classsystem does not care about file format conversion, headercompatibilities, internal data format issues, header/body archivingissues, and media transformations.

[0327] Fully Exact Steganography

[0328] Prior art steganographic methods currently known to the inventorgenerally involve fully deterministic or “exact” prescriptions forpassing a message. Another way to say this is that it is a basicassumption that for a given message to be passed correctly in itsentirety, the receiver of the information needs to receive the exactdigital data file sent by the sender, tolerating no bit errors or “loss”of data. By definition, “lossy” compression and decompression onempirical signals defeat such steganographic methods. (Prior art, suchas the previously noted Komatsu work, are the exceptions here.)

[0329] The principles of this invention can also be utilized as an exactform of steganography proper. It is suggested that such exact forms ofsteganography, whether those of prior art or those of this invention, becombined with the relatively recent art of the “digital signature”and/or the DSS (digital signature standard) in such a way that areceiver of a given empirical data file can first verify that not onesingle bit of information has been altered in the received file, andthus verify that the contained exact steganographic message has not beenaltered.

[0330] The simplest way to use the principles of this invention in anexact steganographic system is to utilize the previously discussed“designed” master noise scheme wherein the master snowy code is notallowed to contain zeros. Both a sender and a receiver of informationwould need access to BOTH the master snowy code signal AND the originalunencoded original signal. The receiver of the encoded signal merelysubtracts the original signal giving the difference signal and thetechniques of simple polarity checking between the difference signal andthe master snowy code signal, data sample to data sample, producing thepassed message a single bit at a time. Presumably data samples withvalues near the “rails” of the grey value range would be skipped (suchas the values 0, 1, 254 and 255 in 8-bit depth empirical data).

[0331] Statistical Steganography

[0332] The need for the receiver of a steganographic embedded data fileto have access to the original signal can be removed by turning to whatthe inventor refers to as “statistical steganography.” In this approach,the methods of this invention are applied as simple a priori rulesgoverning the reading of an empirical data set searching for an embeddedmessage. This method also could make good use of it in combination withprior art methods of verifying the integrity of a data file, such aswith the DSS. (See, e.g., Walton, “Image Authentication for a SlipperyNew Age,” Dr. Dobb's Journal, April, 1995, p. 18 for methods ofverifying the sample-by-sample, bit-by-bit, integrity of a digitalimage.)

[0333] Statistical steganography posits that a sender and receiver bothhave access to the same master snowy code signal. This signal can beentirely random and securely transmitted to both parties, or generatedby a shared and securely transmitted lower order key which generates alarger quasi-random master snowy code signal. It is a priori definedthat 16 bit chunks of a message will be passed within contiguous 1024sample blocks of empirical data, and that the receiver will use dotproduct decoding methods as outlined in this disclosure. The sender ofthe information pre-checks that the dot product approach indeed producesthe accurate 16 bit values (that is, the sender pre-checks that thecross-talk between the carrier image and the message signal is not suchthat the dot product operation will produce an unwanted inversion of anyof the 16 bits). Some fixed number of 1024 sample blocks are transmittedand the same number times 16 bits of message is therefore transmitted.DSS techniques can be used to verify the integrity of a message when thetransmitted data is known to only exist in digital form, whereasinternal checksum and error correcting codes can be transmitted insituations where the data may be subject to change and transformation inits transmission. In this latter case, it is best to have longer blocksof samples for any given message content size (such as 10K samples for a16 bit message chunk, purely as an example).

[0334] NETWORK LINKING METHOD USING INFORMATION EMBEDDED IN DATA OBJECTSTHAT HAVE INHERENT NOISE

[0335] The diagram of FIG. 27 illustrates the aspect of the inventionthat provides a network linking method using information embedded indata objects that have inherent noise. In one sense, this aspect is anetwork navigation system and, more broadly, a massively distributedindexing system that embeds addresses and indices directly within dataobjects themselves. As noted, this aspect is particularly well-adaptedfor establishing hot links with pages presented on the World Wide Web(WWW). A given data object effectively contains both a graphicalrepresentation and embedded URL address.

[0336] As in previous embodiments, this embedding is carried out so thatthe added address information does not affect the core value of theobject so far as the creator and audience are concerned. As aconsequence of such embedding, only one class of data objects is presentrather than the two classes (data object and discrete header file) thatare attendant with traditional WWW links. The advantages of reducing ahot-linked data object to a single class were mentioned above, and areelaborated upon below. In one preferred embodiment of the invention, theWorld Wide Web is used as a preexisting hot link based network. Thecommon apparatus of this system is networked computers and computermonitors displaying the results of interactions when connected to theweb. This embodiment of the invention contemplates steganographicallyembedding URL or other address-type information directly into images,videos, audio, and other forms of data objects that are presented to aweb site visitor, and which have “gray scale” or “continuous tones” or“gradations” and, consequently, inherent noise. As noted above, there isa variety of ways to realize a basic steganographic implementation, allof which could be employed to carry out the present invention.

[0337] With particular reference to FIG. 27, images, quasi-continuoustone graphics, multimedia video and audio data are currently the basicbuilding blocks of many sites 1002, 1004 on the World Wide Web. Suchdata will be hereafter collectively referred to as creative data filesor data objects. For illustrative purposes, a continuous-tone graphicdata object 1006 (diamond ring with background) is depicted in FIG. 27.

[0338] Web site tools—both those that develop web sites 1008 and thosethat allow browsing them 1010—routinely deal with the various fileformats in which these data objects are packaged. It is already commonto distribute and disseminate these data objects 1006 as widely aspossible, often with the hope on a creator's part to sell the productsrepresented by the objects or to advertise creative services (e.g., anexemplary photograph, with an 800 phone number displayed within it,promoting a photographer's skills and service). Using the methods ofthis invention, individuals and organizations who create and disseminatesuch data objects can embed an address link that leads right back totheir own node on a network, their own site on the WWW.

[0339] A user at one site 1004 needs merely to point and click at thedisplayed object 1006. The browser 1010 identifies the object as a hotlink object. The browser reads the URL address that is embedded withinthe object and routes the user to the linked web site 1002, just as ifthe user had used a conventional web link. That linked site 1002 is thehome page or network node of the creator of the object 1006, whichcreator may be a manufacturer. The user at the first site 1004 is thenpresented with, for example, an order form for purchasing the productrepresented by the object 1006.

[0340] It will be appreciated that the creators of objects 1006 havingembedded URL addresses or indices (which objects may be referred to as“hot objects”) and the manufacturers hoping to advertise their goods andservices can now spread their creative content like dandelion seeds inthe wind across the WWW, knowing that embedded within those seeds arelinks back to their own home page.

[0341] It is contemplated that the object 1006 may include a visibleicon 1012 (such as the exemplary “HO” abbreviation shown in FIG. 27)incorporated as part of the graphic. The icon or other subtle indiciawould apprise the user that the object is a hot object, carrying theembedded URL address or other information that is accessible via thebrowser 1010.

[0342] Any human-perceptible indicium (e.g., a short musical tone) canserve the purpose of apprising the user of the hot object. It iscontemplated, however, that no such indicium is required. A user'strial-and-error approach to clicking on a data object having no embeddedaddress will merely cause the browser to look for, but not find, the URLaddress.

[0343] The automation process inherent in the use of this aspect of theinvention is very advantageous. Browsers and web site development toolssimply need to recognize this new class of embedded hot links (hotobjects), operating on them in real time. Conventional hot links can bemodified and supplemented simply by “uploading” a hot object into a website repository, never requiring a web site programmer to do a thingother than basic monitoring of traffic.

[0344] A preferred method of implementing the above described functionsof the present invention generally involves the steps of (1) creating aset of standards by which URL addresses are steganographically embeddedwithin images, video, audio, and other forms of data objects; and (2)designing web site development tools and web browsers such that theyrecognize this new type of data object (the hot object), the tools beingdesigned such that when the objects are presented to a user and thatuser points and clicks on such an object, the web site browser toolknows how to read or decode the steganographic information and route theuser to the decoded URL address.

[0345] The foregoing portions of this description detailed a preferredsteganographic implementation (see, generally, FIG. 2 and the textassociated therewith) that is readily adapted to carry out the presentinvention. In this regard, the otherwise conventional site developmenttool 1008 is enhanced to include, for example, the capability to encodea bit-mapped image file with an identification code (URL address, forexample) according to the present invention. In the present embodiment,it is contemplated that the commercial or transaction based hot objectsmay be steganographically embedded with URL addresses (or otherinformation) using any of the universal codes described above.

[0346] The foregoing portions of this description also detailed apreferred technique for reading or decoding steganographically embeddedinformation (see, generally, FIG. 3 and the text associated therewith)that is readily adapted to carry out the present invention. In thisregard, the otherwise conventional browser 1010 is enhanced to include,for example, the capability to analyze encoded bit-mapped files andextract the identification code (URL address, for example).

[0347] While a preferred implementation for steganographically embeddinginformation on a data object has been described in connection with thepresent invention, one of ordinary skill will appreciate that any one ofthe multitude of available steganographic techniques may be employed tocarry out the function of the present embodiment.

[0348] It will be appreciated that the present embodiment provides animmediate and common sense mechanism whereby some of the fundamentalbuilding blocks of the WWW, namely images and sound, can also become hotlinks to other web sites. Also, the programming of such hot objects canbecome fully automated merely through the distribution and availabilityof images and audio. No real web site programming is required. Thepresent embodiment provides for the commercial use of the WWW in such away that non-programmers can easily spread their message merely bycreating and distributing creative content (herein, hot objects).

[0349] As noted, one can also transition web based hot links themselvesfrom a more arcane text based interface to a more natural image basedinterface.

[0350] Encapsulated Hot Link File Format

[0351] As noted above, once steganographic methods of hot linknavigation take hold, then, as new file formats and transmissionprotocols develop, more traditional methods of “header-based”information attachment can enhance the basic approach built by asteganographic-based system. One way to begin extending thesteganographic based hot link method back into the more traditionalheader-based method is to define a new class of file format which couldeffectively become the standard class used in network navigationsystems. It will be seen that objects beyond images, audio and the likecan now become “hot objects”, including text files, indexed graphicfiles, computer programs, and the like.

[0352] The encapsulated hot link (EHL) file format simply is a smallshell placed around a large range of preexisting file formats. The EHLheader information takes only the first N bytes of a file, followed by afull and exact file in any kind of industry standard format. The EHLsuper-header merely attaches the correct file type, and the URL addressor other index information associating that object to other nodes on anetwork or other databases on a network.

[0353] It is possible that the EHL format could be the method by whichthe steganographic methods are slowly replaced (but probably nevercompletely). The slowness pays homage to the idea that file formatstandards often take much longer to create, implement, and get everybodyto actually use (if at all). Again, the idea is that an EHL-like formatand system built around it would bootstrap onto a system setup based onsteganographic methods.

[0354] The “Noise” in Vector Graphics and Very-Low-Order IndexedGraphics

[0355] The methods of this disclosure generally posit the existence of“empirical signals,” which is another way of saying signals which havenoise contained within them almost by definition. There are two classesof 2 dimensional graphics which are not generally considered to havenoise inherent in them: vector graphics and certain indexed bit-mappedgraphics. Vector graphics and vector graphic files are generally fileswhich contain exact instructions for how a computer or printer drawslines, curves and shapes. A change of even one bit value in such a filemight change a circle to a square, as a very crude example. In otherwords, there is generally no “inherent noise” to exploit within thesefiles. Indexed bit-mapped graphics refers to images which are composedof generally a small number of colors or grey values, such as 16 in theearly CGA displays on PC computers. Such “very-low-order” bit-mappedimages usually display graphics and cartoons, rather than being used inthe attempted display of a digital image taken with a camera of thenatural world. These types of very-low-order bit-mapped mapped graphicsalso are generally not considered to contain “noise” in the classicsense of that term. The exception is where indexed graphic files doindeed attempt to depict natural imagery, such as with the GIF (graphicinterchange format of Compuserve), where the concept of “noise” is stillquite valid and the principles of this invention still quite valid.These latter forms often use dithering (similar to pointillist paintingsand color newspaper print) to achieve near lifelike imagery.

[0356] This section concerns this class of 2 dimensional graphics whichtraditionally do not contain “noise.” This section takes a brief look athow the principles of this invention can still be applied in somefashion to such creative material.

[0357] The easiest way to apply the principles of this invention tothese “noiseless” graphics is to convert them into a form which isamenable to the application of the principles of this invention. Manyterms have been used in the industry for this conversion, including“ripping” a vector graphic (raster image processing) such that a vectorgraphic file is converted to a greyscale pixel-based raster image.Programs such as Photoshop by Adobe have such internal tools to convertvector graphic files into RGB or greyscale digital images. Once thesefiles are in such a form, the principles of this invention can beapplied in a straightforward manner. Likewise, very-low-indexed bitmapscan be converted to an RGB digital image or an equivalent. In the RGBdomain, the signatures can be applied to the three color channels inappropriate ratios, or the RGB image can be simply converted into agreyscale/chroma format such as “Lab” in Photoshop, and the signaturescan be applied to the “Lightness channel” therein. Since most of thedistribution media, such as videotapes, CD-ROMs, MPEG video, digitalimages, and print are all in forms which are amenable to the applicationof the principles of this invention, this conversion from vector graphicform and very-low-order graphic form is often done in any event.

[0358] Another way to apply the principles of this invention to vectorgraphics and very-low-order bitmapped graphics is to recognize that,indeed, there are certain properties to these inherent graphic formatswhich—to the eye—appear as noise. The primary example is the borders andcontours between where a given line or figure is drawn or not drawn, orexactly where a bit-map changes from green to blue. In most cases, ahuman viewer of such graphics will be keenly aware of any attempts to“modulate signature signals” via the detailed and methodical changing ofthe precise contours of a graphic object. Nevertheless, such encoding ofthe signatures is indeed possible. The distinction between this approachand that disclosed in the bulk of this disclosure is that now thesignatures must ultimately derive from what already exists in a givengraphic, rather than being purely and separately created and added intoa signal. This disclosure points out the possibilities here nonetheless.The basic idea is to modulate a contour, a touch right or a touch left,a touch up or a touch down, in such a way as to communicate an N-bitidentification word. The locations of the changes contours would becontained in an analogous master noise image, though now the noise wouldbe a record of random spatial shifts one direction or another,perpendicular to a given contour. Bit values of the N-bit identificationword would be encoded, and read, using the same polarity checking methodbetween the applied change and the change recorded in the master noiseimage.

[0359] Plastic Credit and Debit Card Systems Based on the Principles ofthe Invention

[0360] Growth in the use of plastic credit cards, and more recentlydebit cards and ATM cash cards, needs little introduction. Nor doesthere need to be much discussion here about the long history of fraudand illicit uses of these financial instruments. The development of thecredit card hologram, and its subsequent forgery development, nicelyserves as a historic example of the give and take of plastic cardsecurity measures and fraudulent countermeasures. This section willconcern itself with how the principles of this invention can be realizedin an alternative, highly fraud-proof yet cost effective plasticcard-based financial network.

[0361] A basic list of desired features for an ubiquitous plasticeconomy might be as follows: 1) A given plastic financial card iscompletely impossible to forge; 2) An attempted forged card (a“look-alike”) cannot even function within a transaction setting; 3)Intercepted electronic transactions by a would-be thief would not in anyway be useful or re-useable; 4) In the event of physical theft of anactual valid card, there are still formidable obstacles to a thief usingthat card; and 5) The overall economic cost of implementation of thefinancial card network is equal to or less than that of the currentinternational credit card networks, i.e., the fully loaded cost pertransaction is equal to or less than the current norm, allowing forhigher profit margins to the implementors of the networks. Apart fromitem 5, which would require a detailed analysis of the engineering andsocial issues involved with an all out implementation strategy, thefollowing use of the principles of this invention may well achieve theabove list, even item 5.

[0362]FIGS. 22 through 26, along with the ensuing written material,collectively outline what is referred to in FIG. 26 as “TheNegligible-Fraud Cash Card System.” The reason that the fraud-preventionaspects of the system are highlighted in the title is that fraud, andthe concomitant lost revenue therefrom, is apparently a central problemin today's plastic card based economies. The differential advantages anddisadvantages of this system relative to current systems will bediscussed after a preferred embodiment is presented.

[0363]FIG. 22 illustrates the basic unforgeable plastic card which isquite unique to each and every user. A digital image 940 is taken of theuser of the card. A computer, which is hooked into the centralaccounting network, 980, depicted in FIG. 26, receives the digital image940, and after processing it (as will be described surrounding FIG. 24)produces a final rendered image which is then printed out onto thepersonal cash card 950. Also depicted in FIG. 22 is a straightforwardidentification marking, in this case a bar code 952, and optionalposition fiducials which may assist in simplifying the scanningtolerances on the Reader 958 depicted in FIG. 23.

[0364] The short story is that the personal cash card 950 actuallycontains a very large amount of information unique to that particularcard. There are no magnetic strips involved, though the same principlescan certainly be applied to magnetic strips, such as an implantedmagnetic noise signal (see earlier discussion on the “fingerprinting” ofmagnetic strips in credit cards; here, the fingerprinting would beprominent and proactive as opposed to passive). In any event, the uniqueinformation within the image on the personal cash card 950 is storedalong with the basic account information in a central accountingnetwork, 980, FIG. 26. The basis for unbreakable security is that duringtransactions, the central network need only query a small fraction ofthe total information contained on the card, and never needs to querythe same precise information on any two transactions. Hundreds if notthousands or even tens of thousands of unique and secure “transactiontokens” are contained within a single personal cash card. Would-bepirates who went so far as to pick off transmissions of either encryptedor even unencrypted transactions would find the information uselessthereafter. This is in marked distinction to systems which have a singlecomplex and complete “key” (generally encrypted) which needs to beaccessed, in its entirety, over and over again. The personal cash cardon the other hand contains thousands of separate and secure keys whichcan be used once, within milliseconds of time, then forever thrown away(as it were). The central network 980 keeps track of the keys and knowswhich have been used and which haven't.

[0365]FIG. 23 depicts what a typical point-of-sale reading device, 958,might look like. Clearly, such a device would need to be manufacturableat costs well in line with, or cheaper than, current cash registersystems, ATM systems, and credit card swipers. Not depicted in FIG. 23are the innards of the optical scanning, image processing, and datacommunications components, which would simply follow normal engineeringdesign methods carrying out the functions that are to be describedhenceforth and are well within the capability of artisans in thesefields. The reader 958 has a numeric punch pad 962 on it, showing that anormal personal identification number system can be combined with theoverall design of this system adding one more conventional layer ofsecurity (generally after a theft of the physical card has occurred). Itshould also be pointed out that the use of the picture of the user isanother strong (and increasingly common) security feature intended tothwart after-theft and illicit use. Functional elements such as theoptical window, 960, are shown, mimicking the shape of the card,doubling as a centering mechanism for the scanning. Also shown is thedata line cable 966 presumably connected either to a proprietor'scentral merchant computer system or possibly directly to the centralnetwork 980. Such a reader may also be attached directly to a cashregister which performs the usual tallying of purchased items. Perhapsoverkill on security would be the construction of the reader, 958, as atype of Faraday cage such that no electronic signals, such as the rawscan of the card, can emanate from the unit. The reader 958 does need tocontain, preferably, digital signal processing units which will assistin swiftly calculating the dot product operations described henceforth.It also should contain local read-only memory which stores a multitudeof spatial patterns (the orthogonal patterns) which will be utilized inthe “recognition” steps outlined in FIG. 25 and its discussion. Asrelated in FIG. 23, a consumer using the plastic card merely placestheir card on the window to pay for a transaction. A user could choosefor themselves if they want to use a PIN number or not. Approval of thepurchase would presumably happen within seconds, provided that thesignal processing steps of FIG. 25 are properly implemented witheffectively parallel digital processing hardware.

[0366]FIG. 24 takes a brief look at one way to process the raw digitalimage, 940, of a user into an image with more useful information contentand uniqueness. It should be clearly pointed out that the raw digitalimage itself could in fact be used in the following methods, but thatplacing in additional orthogonal patterns into the image cansignificantly increase the overall system. (Orthogonal means that, if agiven pattern is multiplied by another orthogonal pattern, the resultingnumber is zero, where “multiplication of patterns” is meant in the senseof vector dot products; these are all familiar terms and concepts in theart of digital image processing). FIG. 24 shows that the computer 942can, after interrogating the raw image 970, generate a master snowyimage 972 which can be added to the raw image 970 to produce a yet-moreunique image which is the image that is printed onto the actual personalcash card, 950. The overall effect on the image is to “texturize” theimage. In the case of a cash card, invisibility of the master snowypattern is not as much of a requirement as with commercial imagery, andone of the only criteria for keeping the master snowy image somewhatlighter is to not obscure the image of the user. The central network,980, stores the final processed image in the record of the account ofthe user, and it is this unique and securely kept image which is thecarrier of the highly secure “throw-away transaction keys.” This imagewill therefore be “made available” to all duly connected point-of-salelocations in the overall network. As will be seen, none of thepoint-of-sale locations ever has knowledge of this image, they merelyanswer queries from the central network.

[0367]FIG. 25 steps through a typical transaction sequence. The figureis laid out via indentations, where the first column are steps performedby the point-of-sale reading device 958, the second column hasinformation transmission steps communicated over the data line 966, andthe third column has steps taken by the central network 980 which hasthe secured information about the user's account and the user's uniquepersonal cash card 950. Though there is some parallelism possible in theimplementation of the steps, as is normally practiced in the engineeringimplementation of such systems, the steps are nevertheless laid outaccording to a general linear sequence of events.

[0368] Step one of FIG. 25 is the standard “scanning” of a personal cashcard 950 within the optical window 960. This can be performed usinglinear optical sensors which scan the window, or via a two dimensionaloptical detector array such as a CCD. The resulting scan is digitizedinto a grey scale image and stored in an image frame memory buffer suchas a “framegrabber,” as is now common in the designs of optical imagingsystems. Once the card is scanned, a first image processing step wouldprobably be locating the four fiducial center points, 954, and usingthese four points to guide all further image processing operations (i.e.the four fiducials “register” the corresponding patterns and barcodes onthe personal cash card). Next, the barcode ID number would be extractedusing common barcode reading image processing methods. Generally, theuser's account number would be determined in this step.

[0369] Step two of FIG. 25 is the optional typing in of the PIN number.Presumably most users would opt to have this feature, except those userswho have a hard time remembering such things and who are convinced thatno one will ever steal their cash card.

[0370] Step three of FIG. 25 entails connecting through a data line tothe central accounting network and doing the usual communicationshandshaking as is common in modem-based communications systems. Thepreferred embodiment of this system would obviate the need for standardphone lines, such as the use of optical fiber data links, but for now wecan assume it is a garden variety belltone phone line and that thereader 958 hasn't forgotten the phone number of the central network.

[0371] After basic communications are established, step four shows thatthe point-of-sale location transmits the ID number found in step 1,along with probably an encrypted version of the PIN number (for addedsecurity, such as using the ever more ubiquitous RSA encryptionmethods), and appends the basic information on the merchant who operatesthe point-of-sale reader 958, and the amount of the requestedtransaction in monetary units.

[0372] Step five has the central network reading the ID number, routingthe information accordingly to the actual memory location of that user'saccount, thereafter verifying the PIN number and checking that theaccount balance is sufficient to cover the transaction. Along the way,the central network also accesses the merchant's account, checks that itis valid, and readies it for an anticipated credit.

[0373] Step six begins with the assumption that step five passed allcounts. If step five didn't, the exit step of sending a NOT OK back tothe merchant is not depicted. So, if everything checks out, the centralnetwork generates twenty four sets of sixteen numbers, where all numbersare mutually exclusive, and in general, there will be a large but quitedefinitely finite range of numbers to choose from. FIG. 25 posits therange being 64K or 65536 numbers. It can be any practical number,actually. Thus, set one of the twenty four sets might have the numbers23199, 54142, 11007, 2854, 61932, 32879, 38128, 48107, 65192, 522,55723, 27833, 19284, 39970, 19307, and 41090, for example. The next setwould be similarly random, but the numbers of set one would be offlimits now, and so on through the twenty four sets. Thus, the centralnetwork would send (16×24×2 bytes) of numbers or 768 bytes. The actualamount of numbers can be determined by engineering optimization ofsecurity versus transmission speed issues. These random numbers areactually indexes to a set of 64K universally a priori defined orthogonalpatterns which are well known to both the central network and arepermanently stored in memory in all of the point-of-sale readers. Aswill be seen, a would-be thiefs knowledge of these patterns is of nouse.

[0374] Step seven then transmits the basic “OK to proceed” message tothe reader, 958, and also sends the 24 sets of 16 random index numbers.

[0375] Step eight has the reader receiving and storing all thesenumbers. Then the reader, using its local microprocessor and customdesigned high speed digital signal processing circuitry, steps throughall twenty four sets of numbers with the intention of deriving 24distinct floating point numbers which it will send back to the centralnetwork as a “one time key” against which the central network will checkthe veracity of the card's image. The reader does this by first addingtogether the sixteen patterns indexed by the sixteen random numbers of agiven set, and then performing a common dot product operation betweenthe resulting composite pattern and the scanned image of the card. Thedot product generates a single number (which for simplicity we can calla floating point number). The reader steps through all twenty four setsin like fashion, generating a unique string of twenty four floatingpoint numbers.

[0376] Step nine then has the reader transmitting these results back tothe central network.

[0377] Step ten then has the central network performing a check on thesereturned twenty four numbers, presumably doing its own exact samecalculations on the stored image of the card that the central networkhas in its own memory. The numbers sent by the reader can be“normalized,” meaning that the highest absolute value of the collectivetwenty four dot products can divided by itself (its unsigned value), sothat brightness scale issues are removed. The resulting match betweenthe returned values and the central network's calculated values willeither be well within given tolerances if the card is valid, and way offif the card is a phony or if the card is a crude reproduction.

[0378] Step eleven then has the central network sending word whether ornot the transaction was OK, and letting the customer know that they cango home with their purchased goods.

[0379] Step twelve then explicitly shows how the merchant's account iscredited with the transaction amount.

[0380] As already stated, the primary advantage of this plastic cardinvention is to significantly reduce fraud, which apparently is a largecost to current systems. This system reduces the possibility of fraudonly to those cases where the physical card is either stolen or verycarefully copied. In both of these cases, there still remains the PINsecurity and the user picture security (a known higher security than lowwage clerks analyzing signatures). Attempts to copy the card must beperformed through “temporary theft” of the card, and requirephoto-quality copying devices, not simple magnetic card swipers. Thesystem is founded upon a modem 24 hour highly linked data network.Illicit monitoring of transactions does the monitoring party no usewhether the transmissions are encrypted or not.

[0381] It will be appreciated that the foregoing approach to increasingthe security of transactions involving credit and debit card systems isreadily extended to any photograph-based identification system.Moreover, the principles of the present invention may be applied todetect alteration of photo ID documents, and to generally enhance theconfidence and security of such systems. In this regard, reference ismade to FIG. 28, which depicts a photo-ID card or document 1000 whichmay be, for example, a passport or visa, driver's license, credit card,government employee identification, or a private industry identificationbadge. For convenience, such photograph-based identification documentswill be collectively referred to as photo ID documents.

[0382] The photo ID document includes a photograph 1010 that is attachedto the document 1000. Printed, human-readable information 1012 isincorporated in the document 1000, adjacent to the photograph 1010.Machine readable information, such as that known as “bar code” may alsobe included adjacent to the photograph.

[0383] Generally, the photo ID document is constructed so that tamperingwith the document (for example, swapping the original photograph withanother) should cause noticeable damage to the card. Nevertheless,skilled forgerers are able to either alter existing documents ormanufacture fraudulent photo ID documents in a manner that is extremelydifficult to detect.

[0384] As noted above, the present invention enhances the securityassociated with the use of photo ID documents by supplementing thephotographic image with encoded information (which information may ormay not be visually perceptible), thereby facilitating the correlationof the photographic image with other information concerning the person,such as the printed information 1012 appearing on the document 1000.

[0385] In one embodiment of this aspect of the invention, the photograph1010 may be produced from a raw digital image to which is added a mastersnowy image as described above in connection with FIGS. 22-24. Theabove-described central network and point-of-sale reading device (whichdevice, in the present embodiment, may be considered as a point-of-entryor point-of-security photo ID reading device), would essentially carryout the same processing as described with that embodiment, including thecentral network generation of unique numbers to serve as indices to aset of defined orthogonal patterns, the associated dot product operationcarried out by the reader, and the comparison with a similar operationcarried out by the central network. If the numbers generated from thedot product operation carried out by the reader and the central networkmatch, in this embodiment, the network sends the OK to the reader,indicating a legitimate or unaltered photo ID document.

[0386] In another embodiment of this aspect of the invention, thephotograph component 1010 of the identification document 1000 may bedigitized and processed so that the photographic image that isincorporated into the photo ID document 1000 corresponds to the“distributable signal” as defined above. In this instance, therefore,the photograph includes a composite, embedded code signal, imperceptibleto a viewer, but carrying an N-bit identification code. It will beappreciated that the identification code can be extracted from the photousing any of the decoding techniques described above, and employingeither universal or custom codes, depending upon the level of securitysought.

[0387] It will be appreciated that the information encoded into thephotograph may correlate to, or be redundant with, the readableinformation 1012 appearing on the document. Accordingly, such a documentcould be authenticated by placing the photo ID document on a scanningsystem, such as would be available at a passport or visa control point.The local computer, which may be provided with the universal code forextracting the identification information, displays the extractedinformation on the local computer screen so that the operator is able toconfirm the correlation between the encoded information and the readableinformation 1012 carried on the document.

[0388] It will be appreciated that the information encoded with thephotograph need not necessarily correlate with other information on anidentification document. For example, the scanning system may need onlyto confirm the existence of the identification code so that the user maybe provided with a “go” or “no go” indication of whether the photographhas been tampered with. It will also be appreciated that the localcomputer, using an encrypted digital communications line, could send apacket of information to a central verification facility, whichthereafter returns an encrypted “go” or “no go” indication.

[0389] In another embodiment of the present invention, it iscontemplated that the identification code embedded in the photograph maybe a robust digital image of biometric data, such as a fingerprint ofthe card bearer, which image, after scanning and display, may beemployed for comparison with the actual fingerprint of the bearer invery high security access points where on-the-spot fingerprintrecognition systems (or retinal scans, etc.) are employed.

[0390] It will be appreciated that the information embedded in thephotograph need not be visually hidden or steganographically embedded.For example, the photograph incorporated into the identification cardmay be a composite of an image of the individual and one-, ortwo-dimensional bar codes. The bar code information would be subject toconventional optical scanning techniques (including internal crosschecks) so that the information derived from the code may be compared,for example, to the information printed on the identification document.

[0391] It is also contemplated that the photographs of ID documentscurrently in use may be processed so that information correlated to theindividual whose image appears in the photograph may be embedded. Inthis regard, the reader's attention is directed to the foregoing portionof this description entitled “Use in Printing, Paper, Documents,Plastic-Coated Identification Cards, and Other Material Where GlobalEmbedded Codes Can Be Imprinted,” wherein there is described numerousapproaches to modulation of physical media that may be treated as“signals” amenable to application of the present invention principles.

[0392] Potential Use of the Invention in the Protection and Control ofSoftware Programs

[0393] The illicit use, copying, and reselling of software programsrepresents a huge loss of revenues to the software industry at large.The prior art methods for attempting to mitigate this problem are verybroad and will not be discussed here. What will be discussed is how theprinciples of this invention might be brought to bear on this hugeproblem. It is entirely unclear whether the tools provided by thisinvention will have any economic advantage (all things considered) overthe existing countermeasures both in place and contemplated.

[0394] The state of technology over the last decade or more has made ita general necessity to deliver a full and complete copy of a softwareprogram in order for that program to function on a user's computer. Ineffect, $X were invested in creating a software program where X islarge, and the entire fruits of that development must be delivered inits entirety to a user in order for that user to gain value from thesoftware product. Fortunately this is generally compiled code, but thepoint is that this is a shaky distribution situation looked at in theabstract. The most mundane (and harmless in the minds of mostperpetrators) illicit copying and use of the program can be performedrather easily.

[0395] This disclosure offers, at first, an abstract approach which mayor may not prove to be economical in the broadest sense (where therecovered revenue to cost ratio would exceed that of most competingmethods, for example). The approach expands upon the methods andapproaches already laid out in the section on plastic credit and debitcards. The abstract concept begins by positing a “large set of uniquepatterns,” unique among themselves, unique to a given product, andunique to a given purchaser of that product. This set of patternseffectively contains thousands and even millions of absolutely unique“secret keys” to use the cryptology vernacular. Importantly anddistinctly, these keys are non-deterministic, that is, they do not arisefrom singular sub-000 or sub-2000 bit keys such as with the RSA keybased systems. This large set of patterns is measured in kilobytes andMegabytes, and as mentioned, is non-deterministic in nature.Furthermore, still at the most abstract level, these patterns are fullycapable of being encrypted via standard techniques and analyzed withinthe encrypted domain, where the analysis is made on only a small portionof the large set of patterns, and that even in the worst case scenariowhere a would-be pirate is monitoring the step-by-step microcodeinstructions of a microprocessor, this gathered information wouldprovide no useful information to the would-be pirate. This latter pointis an important one when it comes to “implementation security” asopposed to “innate security” as will be briefly discussed below.

[0396] So what could be the differential properties of this type of keybased system as opposed to, for example, the RSA cryptology methodswhich are already well respected, relatively simple, etc. etc? Asmentioned earlier, this discussion is not going to attempt a commercialside-by-side analysis. Instead, we'll just focus on the differingproperties. The main distinguishing features fall out in theimplementation realm (the implementation security). One example is thatin single low-bit-number private key systems, the mere local use andre-use of a single private key is an inherently weak link in anencrypted transmission system. >“Encrypted transmission systems” arediscussed here in the sense that securing the paid-for use of softwareprograms will in this discussion require de facto encryptedcommunication between a user of the software and the “bank” which allowsthe user to use the program; it is encryption in the service ofelectronic financial transactions looked at in another light.! Would-behackers wishing to defeat so-called secure systems never attack thefundamental hardwired security (the innate security) of the pristineusage of the methods, they attack the implementation of those methods,centered around human nature and human oversights. It is here, still inthe abstract, that the creation of a much larger key base, which isitself non-deterministic in nature, and which is more geared towardeffectively throw-away keys, begins to “idiot proof” the morehistorically vulnerable implementation of a given secure system. Thehuge set of keys is not even comprehensible to the average holder ofthose keys, and their use of those keys (i.e., the “implementation” ofthose keys) can randomly select keys, easily throw them out after atime, and can use them in a way that no “eavesdropper” will gain anyuseful information in the eavesdropping, especially when well within amillionth of the amount of time that an eavesdropper could “decipher” akey, its usefulness in the system would be long past.

[0397] Turning the abstract to the semi-concrete, one possible newapproach to securely delivering a software product to ONLY the bonafidepurchasers of that product is the following. In a mass economic sense,this new method is entirely founded upon a modest rate realtime digitalconnectivity (often, but not necessarily standard encrypted) between auser's computer network and the selling company's network. At firstglance this smells like trouble to any good marketing person, andindeed, this may throw the baby out with the bathwater if by trying torecover lost revenues, you lose more legitimate revenue along the way(all part of the bottom line analysis). This new method dictates that acompany selling a piece of software supplies to anyone who is willing totake it about 99.8% of its functional software for local storage on auser's network (for speed and minimizing transmission needs). This “freecore program” is entirely unfunctional and designed so that even thecraftiest hackers can't make use of it or “decompile it” in some sense.Legitimate activation and use of this program is performed purely on ainstruction-cycle-count basis and purely in a simple very low overheadcommunications basis between the user's network and the company'snetwork. A customer who wishes to use the product sends payment to thecompany via any of the dozens of good ways to do so. The customer issent, via common shipment methods, or via commonly secured encrypteddata channels, their “huge set of unique secret keys.” If we were tolook at this large set as if it were an image, it would look just likethe snowy images discussed over and over again in other parts of thisdisclosure. (Here, the “signature” is the image, rather than beingimperceptibly placed onto another image). The special nature of thislarge set is that it is what we might call “ridiculously unique” andcontains a large number of secret keys. (The “ridiculous” comes from thesimple math on the number of combinations that are possible with, say 1Megabyte of random bit values, equaling exactly the number that “allones” would give, thus 1 Megabyte being approximately 10 raised to the2,400,000 power, plenty of room for many people having many throwawaysecret keys). It is important to re-emphasize that the purchased entityis literally: productive use of the tool. The marketing of this wouldneed to be very liberal in its allotment of this productivity, sinceper-use payment schemes notoriously turn off users and can lower overallrevenues significantly.

[0398] This large set of secret keys is itself encrypted using standardencryption techniques. The basis for relatively higher “implementationsecurity” can now begin to manifest itself Assume that the user nowwishes to use the software product. They fire up the free core, and thefree core program finds that the user has installed their large set ofunique encrypted keys. The core program calls the company network anddoes the usual handshaking. The company network, knowing the large setof keys belonging to that bonafide user, sends out a query on somesimple set of patterns, almost exactly the same way as described in thesection on the debit and credit cards. The query is such a small set ofthe whole, that the inner workings of the core program do not even needto decrypt the whole set of keys, only certain parts of the keys, thusno decrypted version of the keys ever exist, even within the machinecycles on the local computer itself As can be seen, this does notrequire the “signatures within a picture” methods of the maindisclosure, instead, the many unique keys ARE the picture. The coreprogram interrogates the keys by performing certain dot products, thensends the dot products back to the company's network for verification.See FIG. 25 and the accompanying discussion for typical details on averification transaction. Generally encrypted verification is sent, andthe core program now “enables” itself to perform a certain amount ofinstructions, for example, allowing 100,000 characters being typed intoa word processing program (before another unique key needs to betransmitted to enable another 100,000). In this example, a purchaser mayhave bought the number of instructions which are typically used within aone year period by a single user of the word processor program. Thepurchaser of this product now has no incentive to “copy” the program andgive it to their friends and relatives.

[0399] All of the above is well and fine except for two simple problems.The first problem can be called “the cloning problem” and the second“the big brother problem.” The solutions to these two problems areintimately linked. The latter problem will ultimately become a purelysocial problem, with certain technical solutions as mere tools not ends.

[0400] The cloning problem is the following. It generally applies to amore sophisticated pirate of software rather than the currently common“friend gives their distribution CD to a friend” kind of piracy.Crafty-hacker “A” knows that if she performs a system-state clone of the“enabled” program in its entirety and installs this clone on anothermachine, then this second machine effectively doubles the value receivedfor the same money. Keeping this clone in digital storage, hacker “A”only needs to recall it and reinstall the clone after the first periodis run out, thus indefinitely using the program for a single payment, orshe can give the clone to their hacker friend “B” for a six-pack ofbeer. One good solution to this problem requires, again, a rather welldeveloped and low cost real time digital connectivity between user siteand company enabling network. This ubiquitous connectivity generallydoes not exist today but is fast growing through the Internet and thebasic growth in digital bandwidth. Part and parcel of the “enabling” isa negligible communications cost random auditing function wherein thefunctioning program routinely and irregularly performs handshakes andverifications with the company network. It does so, on average, during acycle which includes a rather small amount of productivity cycles of theprogram. The resulting average productivity cycle is in general muchless than the raw total cost of the cloning process of the overallenabled program. Thus, even if an enabled program is cloned, theusefulness of that instantaneous clone is highly limited, and it wouldbe much more cost effective to pay the asking price of the sellingcompany than to repeat the cloning process on such short time periods.Hackers could break this system for fun, but certainly not for profit.The flip side to this arrangement is that if a program “calls up” thecompany's network for a random audit, the allotted productivity countfor that user on that program is accounted for, and that in cases wherebonafide payment has not been received, the company network simplywithholds its verification and the program no longer functions. We'reback to where users have no incentive to “give this away” to friendsunless it is an explicit gift (which probably is quite appropriate ifthey have indeed paid for it: “do anything you like with it, you paidfor it”).

[0401] The second problem of “big brother” and the intuitivelymysterious “enabling” communications between a user's network and acompany's network would as mentioned be a social and perceptual problemthat should have all manner of potential real and imagined solutions.Even with the best and objectively unbeatable anti-big-brothersolutions, there will still be a hardcore conspiracy theory crowdclaiming it just ain't so. With this in mind, one potential solution isto set up a single program registry which is largely a public ornon-profit institution to handle and coordinate the realtimeverification networks. Such an entity would then have company clients aswell as user clients. An organization such as the Software PublishersAssociation, for example, may choose to lead such an effort.

[0402] Concluding this section, it should be re-emphasized that themethods here outlined require a highly connected distributed system, inother words, a more ubiquitous and inexpensive Internet than exists inmid 1995. Simple trend extrapolation would argue that this is not toofar off from 1995. The growth rate in raw digital communicationsbandwidth also argues that the above system might be more practical,sooner, than it might first appear. (The prospect of interactive TVbrings with it the promise of a fast network linking millions of sitesaround the world.)

[0403] Use of Current Cryptology Methods in Conjunction with thisInvention

[0404] It should be briefly noted that certain implementations of theprinciples of this invention probably can make good use of currentcryptographic technologies. One case in point might be a system wherebygraphic artists and digital photographers perform realtime registrationof their photographs with the copyright office. It might be advantageousto send the master code signals, or some representative portion thereof,directly to a third party registry. In this case, a photographer wouldwant to know that their codes were being transmitted securely and notstolen along the way. In this case, certain common cryptographictransmission might be employed. Also, photographers or musicians, or anyusers of this invention, may want to have reliable time stampingservices which are becoming more common. Such a service could beadvantageously used in conjunction with the principles of thisinvention.

[0405] Details on the Legitimate and Illegitimate Detection and Removalof Invisible Signatures

[0406] In general, if a given entity can recognize the signatures hiddenwithin a given set of empirical data, that same entity can take steps toremove those signatures. In practice, the degree of difficulty betweenthe former condition and the latter condition can be made quite large,fortunately. On one extreme, one could posit a software program which isgenerally very difficult to “decompile” and which does recognitionfunctions on empirical data. This same bit of software could notgenerally be used to “strip” the signatures (without going to extremelengths). On the other hand, if a hacker goes to the trouble ofdiscovering and understanding the “public codes” used within some systemof data interchange, and that hacker knows how to recognize thesignatures, it would not be a large step for that hacker to read in agiven set of signed data and create a data set with the signatureseffectively removed. In this latter example, interestingly enough, therewould often be telltale statistics that signatures had been removed,statistics which will not be discussed here.

[0407] These and other such attempts to remove the signatures we canrefer to as illicit attempts. Current and past evolution of thecopyright laws have generally targeted such activity as coming undercriminal activity and have usually placed such language, along withpenalties and enforcement language, into the standing laws. Presumablyany and all practitioners of this signature technology will go tolengths to make sure that the same kind of a) creation, b) distribution,and c) use of these kinds of illicit removal of copyright protectionmechanisms are criminal offenses subject to enforcement and penalty. Onthe other hand, it is an object of this invention to point out thatthrough the recognition steps outlined in this disclosure, softwareprograms can be made such that the recognition of signatures can simplylead to their removal by inverting the known signatures by the amountequal to their found signal energy in the recognition process (i.e.,remove the size of the given code signal by exact amount found). Bypointing this out in this disclosure, it is clear that such software orhardware which performs this signature removal operation will not only(presumably) be criminal, but it will also be liable to infringement tothe extent that it is not properly licensed by the holders of the(presumably) patented technology.

[0408] The case of legitimate and normal recognition of the signaturesis straightforward. In one example, the public signatures coulddeliberately be made marginally visible (i.e. their intensity would bedeliberately high), and in this way a form of sending out “proof comps”can be accomplished. “Comps” and “proofs” have been used in thephotographic industry for quite some time, where a degraded image ispurposely sent out to prospective customers so that they might evaluateit but not be able to use it in a commercially meaningful way. In thecase of this invention, increasing the intensity of the public codes canserve as a way to “degrade” the commercial value intentionally, thenthrough hardware or software activated by paying a purchase price forthe material, the public signatures can be removed (and possiblyreplaced by a new invisible tracking code or signature, public and/orprivate.

[0409] Monitoring Stations and Monitoring Services

[0410] Ubiquitous and cost effective recognition of signatures is acentral issue to the broadest proliferation of the principles of thisinvention. Several sections of this disclosure deal with this topic invarious ways. This section focuses on the idea that entities such asmonitoring nodes, monitoring stations, and monitoring agencies can becreated as part of a systematic enforcement of the principles of theinvention. In order for such entities to operate, they require knowledgeof the master codes, and they may require access to empirical data inits raw (unencrypted and untransformed) form. (Having access to originalunsigned empirical data helps in finer analyses but is not necessary.)

[0411] Three basic forms of monitoring stations fall out directly fromthe admittedly arbitrarily defined classes of master codes: a privatemonitoring station, a semi-public, and a public. The distinctions aresimply based on the knowledge of the master codes. An example of thefully private monitoring station might be a large photographic stockhouse which decides to place certain basic patterns into its distributedmaterial which it knows that a truly crafty pirate could decipher andremove, but it thinks this likelihood is ridiculously small on aneconomic scale. This stock house hires a part-time person to come in andrandomly check high value ads and other photography in the public domainto search for these relatively easy to find base patterns, as well aschecking photographs that stock house staff members have “spotted” andthink it might be infringement material. The part time person cranksthrough a large stack of these potential infringement cases in a fewhours, and where the base patterns are found, now a more thoroughanalysis takes place to locate the original image and go through thefull process of unique identification as outlined in this disclosure.Two core economic values accrue to the stock house in doing this, valueswhich by definition will outweigh the costs of the monitoring serviceand the cost of the signing process itself The first value is in lettingtheir customers and the world know that they are signing their materialand that the monitoring service is in place, backed up by whateverstatistics on the ability to catch infringers. This is the deterrentvalue, which probably will be the largest value eventually. A generalpre-requisite to this first value is the actual recovered royaltiesderived from the monitoring effort and its building of a track recordfor being formidable (enhancing the first value).

[0412] The semi-public monitoring stations and the public monitoringstations largely follow the same pattern, although in these systems itis possible to actually set up third party services which are givenknowledge of the master codes by clients, and the services merely fishthrough thousands and millions of “creative property” hunting for thecodes and reporting the results to the clients. ASCAP and BMI have“lower tech” approaches to this basic service.

[0413] A large coordinated monitoring service using the principles ofthis invention would classify its creative property supplier clientsinto two basic categories, those that provide master codes themselvesand wish the codes to remain secure and unpublished, and those that usegenerally public domain master codes (and hybrids of the two, ofcourse). The monitoring service would perform daily samplings (checks)of publicly available imagery, video, audio, etc., doing high levelpattern checks with a bank of supercomputers. Magazine ads and imageswould be scanned in for analysis, video grabbed off of commercialchannels would be digitized, audio would be sampled, public Internetsites randomly downloaded, etc. These basic data streams would then befed into an ever-churning monitoring program which randomly looks forpattern matches between its large bank of public and private codes, andthe data material it is checking. A small sub-set, which itself willprobably be a large set, will be flagged as potential match candidates,and these will be fed into a more refined checking system which beginsto attempt to identify which exact signatures may be present and toperform a more fine analysis on the given flagged material. Presumably asmall set would then fall out as flagged match material, owners of thatmaterial would be positively identified and a monitoring report would besent to the client so that they can verify that it was a legitimate saleof their material. The same two values of the private monitoring serviceoutlined above apply in this case as well. The monitoring service couldalso serve as a formal bully in cases of a found and proveninfringement, sending out letters to infringing parties witnessing thefound infringement and seeking inflated royalties so that the infringingparty might avoid the more costly alternative of going to court.

[0414] Method for embedding subliminal registration patterns into imagesand other signals

[0415] The very notion of reading embedded signatures involves theconcept of registration. The underlying master noise signal must beknown, and its relative position needs to be ascertained (registered) inorder to initiate the reading process itself (e.g. the reading of the1's and 0's of the N-bit identification word). When one has access tothe original or a thumbnail of the unsigned signal, this registrationprocess is quite straightforward. When one doesn't have access to thissignal, which is often the case in universal code applications of thistechnology, then different methods must be employed to accomplish thisregistration step. The example of premarked photographic film and paper,where by definition there will never be an “unsigned” original, is aperfect case in point of the latter.

[0416] Many earlier sections have variously discussed this issue andpresented certain solutions. Notably, the section on “simple” universalcodes discusses one embodiment of a solution where a given master codesignal is known a priori, but its precise location (and indeed, itexistence or non-existence) is not known. That particular section wenton to give a specific example of how a very low level designed signalcan be embedded within a much larger signal, wherein this designedsignal is standardized so that detection equipment or reading processescan search for this standardized signal even though its exact locationis unknown. The brief section on 2D universal codes went on to point outthat this basic concept could be extended into 2 dimensions, or,effectively, into imagery and motion pictures. Also, the section onsymmetric patterns and noise patterns outlined yet another approach tothe two dimensional case, wherein the nuances associated with twodimensional scale and rotation were more explicitly addressed. Therein,the idea was not merely to determine the proper orientation and scale ofunderlying noise patterns, but to have information transmitted as well,e.g., the N rings for the N-bit identification word.

[0417] This section now attempts to isolate the sub-problem ofregistering embedded patterns for registration's sake. Once embeddedpatterns are registered, we can then look again at how this registrationcan serve broader needs. This section presents yet another technique forembedding patterns, a technique which can be referred to as “subliminaldigital graticules”. “Graticules”—other words such as fiducials orreticles or hash marks could just as well be used—conveys the idea ofcalibration marks used for the purposes of locating and/or measuringsomething. In this case, they are employed as low level patterns whichserve as a kind of gridding function. That gridding function itself canbe a carrier of 1 bit of information, as in the universal 1 second ofnoise (its absence or presence, copy me, don't copy me), or it cansimply find the orientation and scale of other information, such asembedded signatures, or it can simply orient an image or audio objectitself.

[0418]FIG. 29 and 30 visually summarize the two related methods whichcurrently are the preferred embodiments of subliminal digitalgraticules. As will be discussed, the method of FIG. 29 may have slightpractical advantages over the method outlined in FIG. 30, but bothmethods effectively decompose the problem of finding the orientation ofan image into a series of steps which converge on a solution. Theproblem as a whole can be simply stated as the following: given anarbitrary image wherein a subliminal digital graticule may have beenstamped, then find the scale, rotation, and origin (offset) of thesubliminal digital graticule.

[0419] The beginning point for subliminal graticules is in defining whatthey are. Simply put, they are visual patterns which are directly addedinto other images, or as the case may be, exposed onto photographic filmor paper. The classic double exposure is not a bad analogy, though indigital imaging this specific concept becomes rather stretched. Thesepatterns will generally be at a very low brightness level or exposurelevel, such that when they are combined with “normal” images andexposures, they will effectively be invisible (subliminal) and just asthe case with embedded signatures, they will by definition not interferewith the broad value of the images to which they are added.

[0420]FIGS. 29 and 30 define two classes of subliminal graticules, eachas represented in the spatial frequency domain, also known as the UVplane, 1000. Common two dimensional fourier transform algorithms cantransform any given image into its UV plane conjugate. To be precise,the depictions in FIGS. 29 and 30 are the magnitudes of the spatialfrequencies, whereas it is difficult to depict the phase and magnitudewhich exists at every point.

[0421]FIG. 29 shows the example of six spots in each quadrant along the45 degree lines, 1002. These are exaggerated in this figure, in thatthese spots would be difficult to discern by visual inspection of the UVplane image. A rough depiction of a “typical” power spectrum of anarbitrary image is also shown, 1004. This power spectrum is generally asunique as images are unique. The subliminal graticules are essentiallythese spots. In this example, there are six spatial frequencies combinedalong each of the two 45 degree axes. The magnitudes of the sixfrequencies can be the same or different (we'll touch upon thisrefinement later). Generally speaking, the phases of each are differentfrom the others, including the phases of one 45 degree axis relative tothe other. FIG. 31 depicts this graphically. The phases in this exampleare simply randomly placed between PI and −PI, 1008 and 1010. Only twoaxes are represented in FIG. 31—as opposed to the four separatequadrants, since the phase of the mirrored quadrants are simply PI/2 outof phase with their mirrored counterparts. If we turned up the intensityon this subliminal graticule, and we transformed the result into theimage domain, then we would see a weave-like cross-hatching pattern asrelated in the caption of FIG. 29. As stated, this weave-like patternwould be at a very low intensity when added to a given image. The exactfrequencies and phases of the spectral components utilized would bestored and standardized. These will become the “spectral signatures”that registration equipment and reading processes will seek to measure.

[0422] Briefly, FIG. 30 has a variation on this same general theme. FIG.30 lays out a different class of graticules in that the spectralsignature is a simple series of concentric rings rather than spots alongthe 45 degree axes. FIG. 32 then depicts a quasi-random phase profile asa function along a half-circle (the other half of the circle then beingPI/2 out of phase with the first half). These are simple examples andthere are a wide variety of variations possible in designing the phaseprofiles and the radii of the concentric rings. The transform of thistype of subliminal graticule is less of a “pattern” as with theweave-like graticule of FIG. 29, where it has more of a randomappearance like a snowy image.

[0423] The idea behind both types of graticules is the following: embeda unique pattern into an image which virtually always will be quitedistinct from the imagery into which it will be added, but which hascertain properties which facilitate fast location of the pattern, aswell as accuracy properties such that when the pattern is generallylocated, its precise location and orientation can be found to some highlevel of precision. A corollary to the above is to design the patternsuch that the pattern on average minimally interferes with the typicalimagery into which it will be added, and has maximum energy relative tothe visibility of the pattern.

[0424] Moving on to the gross summary of how the whole process works,the graticule type of FIG. 29 facilitates an image processing searchwhich begins by first locating the rotation axes of the subliminalgraticule, then locating the scale of the graticule, then determiningthe origin or offset. The last step here identifies which axes is whichof the two 45 degree axes by determining phase. Thus even if the imageis largely upside down, an accurate determination can be made. The firststep and the second step can both be accomplished using only the powerspectrum data, as opposed to the phase and magnitude. The phase andmagnitude signals can then be used to “fine tune” the search for thecorrect rotation angle and scale. The graticule of FIG. 30 switches thefirst two steps above, where the scale is found first, then therotation, followed by precise determination of the origin. Those skilledin the art will recognize that determining these outstanding parameters,along two axes, are sufficient to fully register an image. The“engineering optimization challenge” is to maximize the uniqueness andbrightness of the patterns relative to their visibility, whileminimizing the computational overhead in reaching some specified levelof accuracy and precision in registration. In the case of exposingphotographic film and paper, clearly an additional engineering challengeis the outlining of economic steps to get the patterns exposed onto thefilm and paper in the first place, a challenge which has been addressedin previous sections.

[0425] The problem and solution as above defined is what was meant byregistration for registration's sake. It should be noted that there wasno mention made of making some kind of value judgement on whether or nota graticule is indeed being found or not. Clearly, the above steps couldbe applied to images which do not in fact have graticules inside them,the measurements then simply chasing noise. Sympathy needs to beextended to the engineer who is assigned the task of setting “detectionthresholds” for these types of patterns, or any others, amidst theincredibly broad range of imagery and environmental conditions in whichthe patterns must be sought and verified. >Ironically, this is where thepure universal one second of noise stood in a previous section, and thatwas why it was appropriate to go beyond merely detecting or notdetecting this singular signal, i.e. adding additional informationplanes!. Herein is where some real beauty shows up: in the combinationof the subliminal graticules with the now-registered embedded signaturesdescribed in other parts of this disclosure. Specifically, once a“candidate registration” is found—paying due homage to the idea that onemay be chasing noise—then the next logical step is to perform a readingprocess for, e.g., a 64 bit universal code signature. As furtherexample, we can imagine that 44 bits of the 64 bit identification wordare assigned as an index of registered users—serial numbers if you will.The remaining 20 bits are reserved as a hash code—as is well known inencryption arts—on the 44 bit identification code thus found. Thus, inone swoop, the 20 bits serve as the “yes, I have a registered image” or“no, I don't” answer. More importantly, perhaps, this allows for asystem which can allow for maximum flexibility in precisely defining thelevels of “false positives” in any given automated identificationsystem. Threshold based detection will always be at the mercy of aplethora of conditions and situations, ultimately resting on arbitrarydecisions. Give me N coin flips any day.

[0426] Back on point, these graticule patterns must first be added to animage, or exposed onto a piece of film. The program name is“STAMP_IT.C.” This program reads in an arbitrarily sized digital imageand adds a specified graticule to the digital image to produce an outputimage. In the case of film, the graticule pattern would be physicallyexposed onto the film either before, during, or after exposure of theprimary image. All of these methods have wide variations in how theymight be accomplished.

[0427] The searching and registering of subliminal graticules is themore interesting and involved process. This section will first describethe elements of this process, culminating in the generalized flow chartof FIG. 37.

[0428]FIG. 33 depicts the first major “search” step in the registrationprocess for graticules of the type in FIG. 29. A suspect image (or ascan of a suspect photograph) is first transformed in its fourierrepresentation using well known 2D FFT routines. The input image maylook like the one in FIG. 36, upper left image. FIG. 33 conceptuallyrepresents the case where the image and hence the graticules have notbeen rotated, though the following process fully copes with rotationissues. After the suspect image has been transformed, the power spectrumof the transform is then calculated, being simply the square root of theaddition of the two squared moduli. it is also a good idea to perform amild low pass filter operation, such as a 3×3 blur filter, on theresulting power spectrum data, so that later search steps don't needincredibly fine spaced steps. Then the candidate rotation angles from 0through 90 degrees (or 0 to PI/2 in radian) are stepped through. Alongany given angle, two resultant vectors are calculated, the first is thesimple addition of power spectrum values at a given radius along thefour lines emanating from the origin in each quadrant. The second vectoris the moving average of the first vector. Then, a normalized powerprofile is calculated as depicted in both 1022 and 1024, the differencebeing that one plot is along an angle which does not align with thesubliminal graticules, and the other plot does align. The normalizationstipulates that the first vector is the numerator and the second vectoris the denominator in the resultant vector. As can be seen in FIG. 33,1022 and 1024, a series of peaks (which should be “six” instead of“five” as is drawn) develops when the angle aligns along its properdirection. Detection of these peaks can be effected by setting somethreshold on the normalized values, and integrating their total alongthe whole radial line. A plot, 1026, from 0 to 90 degrees is depicted inthe bottom of FIG. 33, showing that the angle 45 degrees contains themost energy. In practice, this signal is often much lower than thatdepicted in this bottom figure, and instead of picking the highest valueas the “found rotation angle,” one can simply find the top few candidateangles and submit these candidates to the next stages in the process ofdetermining the registration. It can be appreciated by those practicedin the art that the foregoing was simply a known signal detectionscheme, and that there are dozens of such schemes that can ultimately becreated or borrowed. The simple requirement of the first stage processis to whittle down the candidate rotation angles to just a few, whereinmore refined searches can then take over.

[0429]FIG. 34 essentially outlines the same type of gross searching inthe power spectral domain. Here instead we first search for the grossscale of the concentric rings, stepping from a small scale through alarge scale, rather than the rotation angle. The graph depicted in 1032is the same normalized vector as in 1022 and 1024, but now the vectorvalues are plotted as a function of angle around a semi-circle. Themoving average denominator still needs to be calculated in the radialdirection, rather than the tangential direction. As can be seen, asimilar “peaking” in the normalized signal occurs when the scannedcircle coincides with a graticule circle, giving rise to the plot 1040.The scale can then be found on the bottom plot by matching the knowncharacteristics of the concentric rings (i.e. their radii) with theprofile in 1040.

[0430]FIG. 35 depicts the second primary step in registering subliminalgraticules of the type in FIG. 29. Once we have found a few rotationcandidates from the methods of FIG. 33, we then take the plots of thecandidate angles of the type of 1022 and 1024 and perform what theinventor refers to as a “scaled kernel” matched filtering operation onthose vectors. The scaled kernel refers to the fact that the kernel inthis case is a known non-harmonic relationship of frequencies,represented as the lines with x's at the top in 1042 and 1044, and thatthe scale of these frequencies is swept through some pre-determinedrange, such as 25% to 400% of some expected scale at 100%. The matchedfilter operation simply adds the resultant multiplied values of thescaled frequencies and their plot counterparts. Those practiced in theart will recognize the similarity of this operation with the very wellknown matched filter operation. The resulting plot of the matched filteroperation will look something like 1046 at the bottom of FIG. 35. Eachcandidate angle from the first step will generate its own such plot, andat this point the highest value of all of the plots will become ourcandidate scale, and the angle corresponding to the highest value willbecome our primary candidate rotation angle. Likewise for graticules ofthe type in FIG. 30, a similar “scaled-kernel” matched filteringoperation is performed on the plot 1040 of FIG. 34. This generallyprovides for a single candidate scale factor. Then, using the storedphase plots 1012, 1014 and 1016 of FIG. 32, a more traditional matchedfiltering operation is applied between these stored plots (as kernels),and the measured phase profiles along the half-circles at the previouslyfound scale.

[0431] The last-step in registering graticules of the type in FIG. 29 isto perform a garden variety matched filter between the known (eitherspectral or spatial) profile of the graticule with the suspect image.Since both the rotation, scale and orientation are now known fromprevious steps, this matched filtering operation is straightforward. Ifthe accuracies and precision of preceding steps have not exceeded designspecifications in the process, then a simple micro-search can beperformed in the small neighborhood about the two parameters scale androtation, a matched filter operation performed, and the highest valuefound will determine a “fine tuned” scale and rotation. In this way, thescale and rotation can be found to within the degree set by the noiseand cross-talk of the suspect image itself. Likewise, once the scale androtation of the graticules of the type in FIG. 30 are found, then astraightforward matched filter operation can complete the registrationprocess, and similar “fine tuning” can be applied.

[0432] Moving on to a variant of the use of the graticules of the typein FIG. 29, FIG. 36 presents the possibility for finding the subliminalgraticules without the need for performing a computationally expensive 2dimensional FFT (fast fourier transform). In situations wherecomputational overhead is a major issue, then the search problem can bereduced to a series of one-dimensional steps. FIG. 36 broadly depictshow to do this. The figure at the top left is an arbitrary image inwhich the graticules of the type of FIG. 29 have been embedded. Startingat angle 0, and finishing with an angle just below 180 degrees, andstepping by, for example 5 degrees, the grey values along the depictedcolumns can be simply added to create a resulting column-integratedscan, 1058. The figure in the top right, 1052, depicts one of the manyangles at which this will be performed. This column-integrated scan thenis transformed into its fourier representation using the lesscomputationally expensive 1 dimensional FFT. This is then turned into amagnitude or “power” plot (the two are different), and a similarnormalized vector version created just like 1022 and 1024 in FIG. 33.The difference now is that as the angle approaches the proper angles ofthe graticules, slowly the tell-tale peaks begin to appear in the 1024like plots, but they generally show up at higher frequencies thanexpected for a given scale, since we are generally slightly off on ourrotation. It remains to find the angle which maximizes the peak signals,thus zooming in on the proper rotation. Once the proper rotation isfound, then the scaled kernel matched filter process can be applied,followed by traditional matched filtering, all as previously described.Again, the sole idea of the “shortcut” of FIG. 36 is to greatly reducethe computational overhead in using the graticules of the type in FIG.29. The inventor has not reduced this method of FIG. 36 to practice andcurrently has no data on precisely how much computational savings, ifany, will be realized. These efforts will be part of applicationspecific development of the method.

[0433]FIG. 37 simply summarizes, in order of major process steps, themethods revolving around the graticules of the type in FIG. 29.

[0434] The foregoing principles find application, for example, inphoto-duplication kiosks. Such devices typically include a lens forimaging a customer-provided original (e.g. a photographic print or film)onto an optoelectronic detector, and a print-writing device for exposingand developing an emulsion substrate (again photographic paper or film)in accordance with the image data gathered by the detector. The detailsof such devices are well known to those skilled in the art, and are notbelabored here.

[0435] In such systems, a memory stores data from the detector, and aprocessor (e.g. a Pentium microprocessor with associated supportcomponents) can be used to process the memory data to detect thepresence of copyright data steganographically encoded therein. If suchdata is detected, the print-writing is interrupted.

[0436] To avoid defeat of the system by manual rotation of the originalimage off-axis, the processor desirably implements the above-describedtechnique to effect automatic registration of the original,notwithstanding scale, rotation, and origin offset factors. If desired,a digital signal processing board can be employed to offload certain ofthe FFT processing from the main (e.g. Pentium) processor. After arotated/scaled image is registered, detection of any steganographicallyencoded copyright notice is straightforward and assures the machine willnot be used in violation of a photographer's copyright.

[0437] While the techniques disclosed above have made use of applicant'spreferred steganographic encoding methods, the principles thereof aremore widely applicable and can be used in many instances in whichautomatic registration of an image is to be effected.

[0438] Use of Embedded Signatures in Video, Wherein a Video Data StreamEffectively Serves as a High-Speed One Way Modem

[0439] Through use of the universal coding system outlined in earliersections, and through use of master snowy frames which change in asimple fashion frame to frame, a simple receiver can be designed suchthat it has pre-knowledge of the changes in the master snowy frames andcan therefore read a changing N-bit message word frame by frame (orI-frame by I-frame as the case may be in MPEG video). In this way, amotion picture sequence can be used as a high speed one-way informationchannel, much like a one-way modem. Consider, for example, a frame ofvideo data with N scan lines which is steganographically encoded toeffect the transmission of an N-bit message. If there are 484 scan linesin a frame (N), and frames change 30 times a second, an informationchannel with a capacity comparable to a 14.4 kilobaud modem is achieved.

[0440] In actual practice, a data rate substantially in excess of N bitsper frame can usually be achieved, yielding transmission rates nearerthat of ISDN circuits.

[0441] Errata

[0442] Applicant is preparing a steganographic marking/decoding“plug-in” for use with Adobe Photoshop software. This software,presented as commented source code, is attached as Appendix B toapplication 08/637,531. The code was written for compilation withMicrosoft's Visual C++ compiler, version 4.0, and can be understood bythose skilled in the art.

[0443] This source code embodies several improvements to the technologydisclosed in applicant's prior applications, both in encoding anddecoding, and also in user interface.

[0444] Applicant's copyrights in this code are reserved, save forpermission to reproduce same as part of the specification of the patent.

[0445] While this software is particularly designed for thesteganographic encoding and decoding of auxiliary data in/fromtwo-dimensional image data, many principles thereof are applicable tothe encoding of digitized audio, as contemplated by the presentlyclaimed invention.

[0446] Before concluding, it may be instructive to review some of theother fields where principles of applicant's technology (both in thisapplication, and prior applications) can be employed.

[0447] One is document security for passports, visas, “green cards,”etc. The photos on such documents can be processed to embed a subliminaldata signal therein, serving to authenticate the document.

[0448] Related to the foregoing are objects (e.g. photos and ID cards)having biometric data embedded therein. One example of such biometricdata is a fingerprint, allowing the authenticity of a person bearingsuch an ID to be checked.

[0449] Another application is smart business cards, wherein a businesscard is provided with a photograph having unobtrusive, machine-readablecontact data embedded therein. (The same function can be achieved bychanging the surface microtopology of the card to embed the datatherein.)

[0450] Yet another promising application is in content regulation.Television signals, images on the internet, and other content sources(audio, image, video, etc.) can have data indicating their“appropriateness” (i.e. their rating for sex, violence, suitability forchildren, etc.) actually embedded in the content itself rather thanexternally associated therewith. Television receivers, web browsers,etc., can discern such appropriateness ratings (e.g. by use of universalcode decoding) and can take appropriate action (e.g. not permittingviewing of an image or video, or play-back of an audio source).

[0451] Credit cards are also likely candidates for enhancement by use ofsteganographic marking, providing an invisible and covert data carrierto extend functionality and improve security.

[0452] The field of merchandise marking is generally well served byfamiliar bar codes and universal product codes. However, in certainapplications, such bar codes are undesirable (e.g. for aestheticconsiderations, or where security is a concern). In such applications,applicant's technology may be used to mark merchandise, either throughin innocuous carrier (e.g. a photograph associated with the product), orby encoding the microtopology of the merchandise's surface, or a labelthereon.

[0453] There are applications—too numerous to detail—in whichsteganography can advantageously be combined with encryption and/ordigital signature technology to provide enhanced security.

[0454] Medical records appear to be an area in which authentication isimportant. Steganographic principles— applied either to film-basedrecords or to the microtopology of documents—can be employed to providesome protection against tampering.

[0455] Many industries, e.g. automobile and airline, rely on tags tomark critical parts. Such tags, however, are easily removed, and canoften be counterfeited. In applications wherein better security isdesired, industrial parts can be steganographically marked to provide aninconspicuous identification/authentication tag.

[0456] In various of the applications reviewed above and in applicant'searlier applications, different messages can be steganographicallyconveyed by different regions of an image (e.g. different regions of animage can provide different internet URLs, or different regions of aphotocollage can identify different photographers). Likewise with othermedia (e.g. sound).

[0457] Some software visionaries look to the data when data blobs willroam the datawaves an interact with other data blobs. In such era, itwill be necessary that such blobs have robust and incorruptible ways toidentify themselves. Steganographic techniques again hold much promisehere.

[0458] Finally, message changing codes—recursive systems in whichsteganographically encoded messages actually change underlyingsteganographic code patterns—offer new levels of sophistication andsecurity. Such message changing codes are particularly well suited toapplications such as plastic cash cards where time-changing elements areimportant to enhance security.

[0459] Again, while applicant prefers the particular forms ofsteganographic encoding, the foregoing applications (and applicationsdisclosed in applicant's prior applications) can be practiced with othersteganographic marking techniques.

[0460] Having described and illustrated the principles of my inventionwith reference to various embodiments thereof, it should be apparentthat the invention can be modified in arrangement and detail withoutdeparting from such principles. Moreover, a variety of enhancements canbe incorporated from the teachings of my prior applications.

[0461] Accordingly, I claim as my invention all such embodiments as comewithin the scope and spirit of the following claims and equivalentsthereto.

I claim:
 1. A method of creating a photocollage, including: providingplural photographic images; encoding each of the photographic imageswith a different steganographic message; the steganographic messagesserving to associate with each photographic image, informationcorresponding thereto; and printing the encoded photographic images on acommon page.
 2. The method of claim 1 in which the information comprisesdata identifying a person associated with the corresponding photographicimage.
 3. The method of claim 2 in which the person is a photographer ofthe photographic image.
 4. The method of claim 1 in which each messageidentifies a corresponding record in a database, each record includinginformation specific to a corresponding photographic image.
 5. Themethod of claim 1 in which the steganographic message conveys pluraldigital bits of information.
 6. The method of claim 1 in which at leastone of the steganographic messages is dispersed across the correspondingphotographic image, rather than being localized in a limited portion. 7.The method of claim 1 in which each steganographic message is encoded inaccordance with pseudo-random noise data.
 8. The method of claim 1 inwhich each of the photographic images comprises pixels, and the encodingchanges the luminance of a majority of the pixels of each photographicimage.
 9. A computer storage medium having stored thereon computerinstructions for performing the method of claim 1 .
 10. A photocollageproduced by the method of claim 1 .
 11. A storage medium havingrepresented thereon a photocollage, the photocollage comprising: pluralphotographic images, each embedded with a different steganographicmessage; the steganographic messages serving to associate with eachphotographic image, information corresponding thereto.
 12. The inventionof claim 11 in which the information comprises data identifying a personassociated with the corresponding photographic image.
 13. The inventionof claim 12 in which the person is a photographer of the photographicimage.
 14. The invention of claim 11 in which each message identifies acorresponding record in a database, each record including informationspecific to a corresponding photographic image.
 15. The invention ofclaim 11 in which the steganographic message conveys plural digital bitsof information.
 16. The invention of claim 11 in which at least one ofthe steganographic messages is dispersed across the correspondingphotographic image, rather than being localized in a limited regionthereon.
 17. The invention of claim 11 in which each steganographicmessage is encoded in accordance with pseudo-random noise data.
 18. Amethod comprising encoding a photograph with a steganographic message,the message serving to identify a corresponding record in a database,the database record detailing information relating to the photograph.19. The method of claim 18 in which the message comprises an indexnumber.
 20. The method of claim 18 in which the information relating tothe photograph includes information identifying a person associated withthe photograph.
 21. The method of claim 20 in which the person is aphotographer of the photographer.
 22. The method of claim 18 in whichthe information relating to the photograph includes contact information,such as an address.
 23. The method of claim 18 in which thesteganographic message conveys plural digital bits of information. 24.The method of claim 18 in which the steganographic message is dispersedacross the photograph, rather than being localized in a limited portion.25. The method of claim 18 in which the steganographic message isencoded in accordance with pseudo-random noise data.
 26. The method ofclaim 18 in which the photograph comprises pixels, and the encodingchanges the luminance of a majority of the pixels.
 27. The method ofclaim 18 in which the steganographic message is a code pre-exposed onemulsion media, onto which media a photographic image is later exposed.28. A computer storage medium having stored thereon computerinstructions for performing the method of claim 18 .
 29. A photographproduced in accordance with the method of claim 18 .
 30. A storagemedium, such as paper, film, or computer storage media, the storagemedium having represented thereon a photograph, characterized in thatthe photograph is encoded with a steganographic message, the messageserving to identify a corresponding record in a database, the databaserecord detailing information relating to the photograph.
 31. Theinvention of claim 30 in which the message comprises an index number.32. The invention of claim 30 in which the information relating to thephotograph includes information identifying a person associated with thephotograph.
 33. The invention of claim 32 in which the person is aphotographer of the photographer.
 34. The invention of claim 30 in whichthe information relating to the photograph includes contact information,such as an address.
 35. The invention of claim 30 in which thesteganographic message conveys plural digital bits of information. 36.The invention of claim 30 in which the steganographic message isdispersed across the photograph, rather than being localized in alimited portion.
 37. The invention of claim 30 in which thesteganographic message is encoded in accordance with pseudo-random noisedata.
 38. The invention of claim 30 in which the photograph comprisespixels, and the encoding changes the luminance of a majority of thepixels.
 39. The invention of claim 30 in which the steganographicmessage is a code pre-exposed on emulsion media, onto which media aphotographic image is later exposed.
 40. A storage medium, such as filmor computer storage media, having represented thereon a medical imageembedded with a steganographic message, the message aiding inauthentication of the medical image.
 41. The invention of claim 40 inwhich the message aids in protecting the medical image againstundetected tampering.
 42. The invention of claim 40 in which thesteganographic message is dispersed across the medical image, ratherthan being localized in a limited portion.
 43. The invention of claim 40in which the steganographic message is encoded in accordance withpseudo-random noise data.
 44. The invention of claim 40 in which themedical image comprises pixels, and the encoding changes the luminanceof a majority of the pixels.